Marketing. "Beauty is in the eye of the beholder." Personally, I'm too old to have ever experienced BMX, so don't "get it" and they look very plain to me. We tend to admire things we can relate to, remember, or are quite simply "eye candy". It's partly an age thing. Take the Bowden for example. You love 'em or hate 'em. I "get" muscle bikes as that's what I grew up with. They emulate hot rods and fast cars.
Early ( pre mid 30's balloon) diamond shaped frames put me to sleep. All of our Canadian bikes looked like that. BMX are cool in that they were raced and tricked and many were made to exotic specs and materials from what I gather. To me, more is more. To some, less is more. I'll take a bicycle that looks like a motorcycle or a space ship, or hot rod over any other design. That's my taste. I like top heavy gals, dagmars if you will, ( not big shoulders) curves, and shiny things, or an item that tells a story with aged beauty.
I commend people that can create a market that doesn't appeal to everyone, but reaps them huge money. Why not? Just because I'm not in that market, or it doesn't appeal to me isn't wrong. I just don't "get it", so make fun of it. All in good taste I hope. Some guys like big bumpers, wide fenders, some don't. Lets all rejoice"Viva la difference"!!