Slot fully booked but people not turning up!!

It took me 3 months to convince my senior citizen parents to get a vaccine shot, recently I got them registered but my mother, still reluctant, did not agree to go first. So, I booked a slot for my dad, after several days of attempt, and he wasn't so sure either and gave me all sorts of rationale, like, " I'll see the situation at the vaccination center." , "If there is a queue then I won't wait.", and so on.. But to his surprise when he reached the center, his imaginations took a back seat as there was hardly anyone, he got in and was asked to wait. After waiting for sometime, on inquiry about the delay, he was informed that only four people turned up for the slot so once a count of ten people are available, they will give him the shot. On trying for another center the case was similar and he had to return home without it.

After I was informed about it, I kept thinking how many other such people, struggling with their thoughts reach to the vaccination centers and have been returned, for the irresponsibility of those not showing up. There could be a system of first come first serve or a waiting list that can give a chance to the once interested and available. The crowd from the high pressure centers can be allocated to the centers with low footfall. Measures can be taken to smoothen vaccination experience by studying the gaps. "Anyway my father could not go the next day, and he is still not vaccinated."

Being a part of the development sector I am widely connected to people with rural background and talking to a few gave me a vague idea that the situation is more or less the same and people are not turning up to the centers despite the full booked slots.I wonder that if such is the case then we as a country will take way longer than estimated to vaccinate the last person. Complete vaccination by end of 2021?