My group of friends would always play Smash. That was our go-to. Everyone pretty much played just because, but for me and this other guy, we at least wanted to go a little further, i.e. we would put some effort into researching and found out about l-cancelling, etc. I can't recall if I had a main at that point, but it would usually be him or I winning the free-for-alls. One day, he picked up Sheik, and I lost my ability to win. He would do these crazy combos and always end with Fair. I got so furious and I think I just started testing every character in the game for a counter. Peach comes out, and immediately I noticed one of her moves were special, her down smash. whenever he would approach, I just flicked my c-stick down and it vortexed him in and dealt over 20%. Keep in mind this was before I knew about concepts such as adaptation, punishment, DI'ing out of multi-hit attacs, etc., and I'm sure he was in a similar boat. I didn't even know about Peach's various idiosyncratic traits like float-cancelling or turnips. Nope, just down smash. I think I wacked him enough with it that he became scared of it, and it made it even worse for him to deal with the spam.
So that was the primary reason I fell in love with Peach. I also liked the fact that Peach is kinda tabuu in casuals with a bunch of guys and it made it funnier that I would win with her. All the things I picked up from her later, such as her float cancel just made me stick with her more.