Maybe so about the Hex and fourplay being suited to street, but the street frames you can get by other makes than trials are very good, also people probaly just like the feel and at the end of the day, it's all down to personal preference.
NS Capital, Suburban, Doberman Molosse, Blkmrkt Riots, all these are amazing frames for street. I know someone that runs street with a fourplay as he alos beleives that trials frames are very good for street;
Fourplay street setup (Pinkbike)
DMR, snappy happy. There parts like cranks, rims and pedals are okay but people I know who have had DMRS and have snapped them (mostly DJ) Just stay away from DMR frames and forks.