If God is Omniscient why we need to visit temples at remote places?

I want to tell a short story here. When Swami Vivekanand was still a Parivrajaka (wandering monk) in India, he visited the court of the Maharaja of Khetri. This young Maharaja was a so-called western-educated, liberal minded new generation of Indian. He decided to discuss his views with the Sanyasi. He said, “Swamiji, don’t you think temples and idol-worship is a little bit of a redundant and unneeded part of our culture?” Swamiji smiled at him silently and didn’t reply immediately. Instead of answering the Maharaja directly, he turned to the Divan (an important minister) of Khetri who was in the same room. He said “Divan Saheb, can you please bring me that portrait of the Maharaja?”

The Divan, confused, complied. He brought the expensive and painstaking portrait of the Maharaja to the waiting Sanyasi. Swamiji took the painting, looked up and down it, and said, “So this is the portrait of the Maharaja, is it not?” The Divan said, “Yes, Swamiji”. Swamiji said, “Well then, it isn’t important, is it? We have the Maharaja right here! Spit on this painting, Divan Saheb!” The Divan looked horrified and backed away. He said, “What are you saying, Swamiji?! This is the portrait of the Maharaja! I couldn’t possibly do that!” Swami Vivekananda smiled and handed the portrait back to the Divan. He turned his attention to the King.

“Do you see now?”, he asked the king. “The Murti in the temple is an icon, which is essentially only a tool for people to feel connected with the divine. It is a walking stick you can put your weight on in your spiritual journey. In and of itself, you are right, the Murti is just a piece of sculpted stone. But when worshipped and loved, its value becomes much higher. Just as this set of brushstrokes, paint and canvas became ‘The Maharaja’, so too does that piece of stone become an icon of divinity when you worship and place your love and affection in it. Therefore, O king, the value of temples is extremely high! Don’t undermine them”

This story is a very crucial concept that is the basis of Vedanta. While Divinity pervades everything, that extreme size and vastness is too hard for any but the most enlightened souls. For instance, us! Can we grasp the concept of infinity; a part of which is also infinity, twice which is also infinity, infinity subtracted from which is infinity? No! The concept is too large and too hard for our simple day-to-day minds to grasp. Therefore, we choose the other ways of getting to know divinity, and worship icons in temples and use our devotion to understand pervasive spirituality. Therefore, the Darshana in the temples, the icons, the Puja, the rituals, the Arati, and all the other aspects are quite important for the common man to get a little bit closer to the Godhead.

The omnipresence of God is a philosophical doctrine and it is illustrated for the simple folk through stories and legends which comprise the mythology. So mythology is the vehicle of philosophy. Visiting temples is not a need it is a want. The very first place where you should practice having your Darshan (vision) of God is within your own heart. And then in the hearts of all other beings. The answer is given in Shrimad Bhagwad Gītā Chapter 6.

"yo mā? pa?yati sarvatra sarva? ca mayi pa?yati | tasyāha? na pra?a?yāmi sa ca me na pra?a?yati " || 30 || He who sees Me everywhere and everything in Me; I am not separated from him and he is never separated from Me. sarva-bhūta-sthita? yo mā? bhajaty-ekatvam-āsthita? | sarvathā vartmāno’pi sa yogī mayi vartate || 31 || 31. The Yogi who, established in unity, worships Me dwelling in all beings, he abides in Me, howsoever he may live. So until and unless you have seen God in your own self and in all other beings visiting temples is pointless.

Another points is that water is everywhere on earth but why you dig a well, Go near to a river, Even install water tank on the top of your home & tap in kitchen & bathroom. Air, No place in the world where it is not available but with the consideration of its purity, coolness, warmness, and other consideration we travel place to place.And on our working place or residence we make more arrangements according to our liking. So simply all these are easily available on earth but to manage them in reach everyone makes efforts to manage that according to its feasibility or requirement. The same god is present everywhere but to meet him everyone has to make some efforts and out of many practices one is to visit temple.

It is all about effect and the satisfactions isn't it?, mentally you feel satisfied after watching a great movie in a great environment, with friends or family, you enjoy isn't it? It is never about God, all is about having some time where you can forget about all the problems in life and get a momentary peace by knowing that "yes, I have said all my issues in life to a person, now I can relax a bit". As simple as that. Same is the case with the temples and other religious shrines. You get to have a nice time with family, friends or if you go alone, a nice place to sit and discover yourself in the solitude. My friend, that is the sole reasons for the temples, moreover, it helps to generate some jobs, many people can rely upon it for winning the bread for their family. Other than this, other reasons as mentioned in the other answers too... And comes some scientific reasons or say pseudoscience ??

You go for darshan in temple, not to see God, but to be seen by God. Of course, if you are completely God conscious, you will see God where ever you go, but to go to the temple is to do a service to God and that will please Him. And it will purify your consciousness, and it will please God to see you take some trouble to go and see Him. And since you are part and parcel of God, when He is pleased, you become pleased.

But the most pleasing you can do for God in this age is to chant his name, and that you can do anywhere. "hare krsna hare krsna krsna krsna hare hare \ hare rama hare rama rama rama hare hare" iti shodasakam namnam kali-kalmasha-nasanam \natah parataropayah sarva-vedeshu drisyate" "This mantra, consisting of 16 words and 32 syllables, is the only means against evil in this age. After searching through all the Vedic literature, one cannot find a method of religion more sublime for this age than the chanting of Hare Krsna." --- Kali-Santarana Upanishad