^Exactly. Back in the day, everyone wore suits. Even at causal dinners or sporting events or even going to see a movie. So the old mobsters did the same. Now days most people hardly ever where them. Hence mobsters dressing more slobbish (and of course keeping a low-profile blah blah blah).

Plus those guys pictured above are lower-level guys, yes? They're not leaders sitting back and collecting money. They're working the streets, so they'll dress accordingly.