Paris Roubaix is a classic, where riders have 1 week of no racing to prepare for. We can’t have 21 stages of Paris Roubaix, obviously…An entertaining large stage is better than an entertaining short stage. Paris Roubaix is an example of that.
Riders also want heavy but short stages. Preferably three 1-HC mountains on a 160km stage than the same thing but an extra 80km of flat. There’s just no need for it