I think the idea is that walking around the city dressed in a heavy suit when it's very hot outside is uncomfortable and sweaty.

I'd argue that requiring your employees to play an archaic game of dress-up is the real problem, but if I'm being honest, it can be pretty uncomfortable to walk around a sweltering city even in street clothes. (That being said I don't think the tradeoff is worth destroying your city with car-centric design)