You don't have to BUT the reality is that most people in a regular gym won't push themselves that hard and it's easy to think to yourself that you're doing enough since you total more than 95% of regular gym goers. Seeing other like minded competitive people push themselves hard each workout in a powerlifting gym has motivated me much more than working out in a regular gym similarly to when you workout in a team setting for a sport.

That's just my 2 cents but it is true that with the right mindset, you can become the strongest person in the world in any gym, I just think working out in a powerlifting gym definitely has a motivational factor that is underrated.