26" vs 700c

Not trying to stir anything up here, just curious.
I dont ride freestyle myself, but I used to ride street on a 26" mtb frame. Ive always wondered why so much development is going into making burlier trick bikes with massive tyre clearance when there are already tonnes of existing mtb street frames that could easily run fixed.
Is it a size/standover height/geometry issue?

thats exactly what i was thinking, seems pointless when these bikes already exist, and are designed better for tricks with lower top tubes