I've never witnessed pressure myself, because I'm dtf.
But picture this: you're in a sea of people giving away gold nuggets, and all you have is silver nuggets. Try and stay busy selling your silver, when gold is thought of as superior.
Some can do it well, others, with little to no personality, cannot.
Most girls who don't do it, already have a good client base and don't need to.
But the rule of thumb is, if you're not busy then bye.
So not required, but if not doing it makes you slow, you won't survive.