At a guess I’d say companies see the offloading of it to an external computer as an easier solution, let the computing experts deal with the computing stuff.
In the meantime we have DJay Pro and a phone/tablet that works very well as DVS setup.
This is actually something I wish so much for the Prime 4/4+ to happen, getting the option to not only use the two phono inputs for vinyl, but also to control Engine deck 3 and 4 via custom DVS, without any extra laptop software needed. This would be a killer USP. One can only dream!
Just plug in jack and put your android tablet to any mixer with Cross Dj app because in settings you have mixer mode to split 2 decks per mixer channel. If you want setup 4 channel mixing just get 2 the same tablets and connect the same way. Its only useful if you don’t own any CDJs players