Yeah, same here. I ran some flavor of 3.x with dozens of groups for over 10 years with just about zero issues. I say just about, because there was one guy who wanted to run his quarter Genie, half Orc, quarter Dragon with 4 classes that gave him a +22 to trip or whatever. It was an easy solution though: I just told him no.
Same here. Some of it too was that the DM had absolute power no matter how much someone min/maxes. So if someone comes to the table with sole intention of "breaking the game", it's not going to go well for them. For instance, show me you get a +13 to hit while the rest of the group is +6, I'm going to say, "No, respec into something that sensical". Refuse, I'll let you keep +13 on your sheet, but you're secretly only hitting at +7. Usually the snickering from the other players each time they missed was enough to clue them in to just pick something else.
Also, throwing fits got you banned from the campaign. Not being angry, but throwing a real temper tantrum. I have zero patience for adult toddlers in my life. Thankfully, only had to do it a few times in my life and always when playing with new people.