Why do people do not play classical games now

Suspected cheating also plays a role.

At short time controls it is harder to cheat and easier to detect. Carlsen said that is the reason he only plays bullet online.

Well as you all say I also play more blitz and bullets but classical I play only once a month when I get bored

But I do not recommend that lichess should put classical because that is least time control everyone play so, lichess should remove classical

Classical is a good choice when you are starting to play and haven't been in similar situations many times before. Then you have to try to calculate what is a good move. After a while you usually have a pretty good idea of what is a good move almost instantly, unless the specific situation is very complicated. When you get to this stage, your rating is probably a little higher. You become a "target" for noobs who are tired of losing and who is looking for a game with someone with a higher rating that they can engine-cheat against to gain some rating-points, so you should move on to shorter time-control. It's pretty easy to catch someone cheating if the timecontrol is a little bit lower, since people don't spend 10 seconds on every single move in rapid and blitz, but cheaters do, since they have to wait to see what the engine says.

As M. Carlsen once said, he usually just "know" what is the right move once he sees his opponent move. The only reason he stops and thinks is to make sure his instincts are right. It's not because he doesn't know what to play.

Well i would play short time controls game because i do not not want to lose against a cheater