Most chess clubs either online or in person will have many more fast (less than 15 minute) games than longer games.
Why aren't standard games the norm on chess.com?

You use the words 'opinion' and 'true'. Those very words vary with whom you speak to. I would say they could vary enough to have so many meanings that to catalogue them all would be Sisyphean in its utility.
I actually think game in 30 is too fast. I play a decent amount of mindless blitz on here, but for serious chess it's OTB for me. We play game in 90 with a 30 second increment at the chess club and I really enjoy that time control.
Well, my personal opinion is that the best, truest way to play chess would be OTB, and each side be given 3 hours. People have to remember that chess, real chess, the way it was meant to be played, is a sport of the mind. Therefore, in order to call yourself a true chess player in my opinion, you have to be able to handle the mental stamina it takes to play for that long of time period.
I tried making an open challenge on chess.com for people to play me in a game or perhaps a series of games of this nature, and I didn't get any takers.
Standard chess (30 mins per side or more) is in my opinion the true way to play chess, and the real measure of one's chess rating. Why is it that on chess.com most people's preferred way of playing is either extremely long games (online chess, 24 hours or more), or blitz chess (10 mins or less)? Why are these types of games so much more popular than standard games?