Why economists use graphs the wrong way

I have encountered the graphs representing supply and demand for the first time more than 15 years ago, in a microeconomics class. Or macroeconomics. Doesn’t matter. Those supply and demand (S&D) graphs are supposed to represent the dependency of quantities of something sold on the market, on the changes in price on the market. Now, at that time I have already graduated in Electrical Engineering, and so have already seen, drawn and analysed quite a lot of graphs. What struck me was the fact that there is a graph showing how quantities change in response to price change - the lecturer has even written a formula Q=f(P) where Q is quantity and P is price, but the graph is drawn the other way around!? The X and Y axes are misplaced, turned the wrong way around. I thought it might be that for the economists the price was all that matters, so it was easy to draw a horizontal line on the graph that denotes price, although the graph is not so easy to understand that way… Or something else, who would know…

The original supply and demand graph from Marshall's "Principles of economics"; Source: wikipedia.org

Today I have discovered who the culprit, in my opinion, of course :), for this situation is. His name is Alfred Marshall (26 July 1842 – 13 July 1924), and he was a British economist who was the first to describe, in his book “Principles of economics”, the relationships between supply and demand, marginal utility and costs of production. For some reason he chose to draw the accompanying graphs in the “wrong” way, which stuck until these days. I forgive him :) because of his undeniable contribution to economics theory.