I remember when no one used flats, back in the '80's and early '90's. At that time flatwound bass strings were something they had in the old days, like rickets and diphtheria. Definitely to be avoided.
It all changed with PIno and that Voodoo album. Nowadays everybody has to have a Precision with flats on. It's become yet another bass playing tyranny.
When I finally got some TI flats about ten years ago it was a revelation how much fun they were to play and how I could now accurately emulate bass parts I'd been playing right but that didn't sound like the original. More than anything, the different attack and decay you get on flats compared to roundwounds made all the difference.