Yup ... mountain bikes went way deeper into development than road bikes .... They started out as old cruisers, basically followed road bike design, and suddenly got popular in a big way, so companies had to compete for customers ... and the R&D departments got busy. Meanwhile, the "gold standard" for road bikes was whatever had been popular a decade earlier ....
Interesting ... I was listening to the rambling reporters during the Paris-Roubais Femmes (I think) broadcast, and they mentioned some brand which had an onboard air system to inflate and deflate the tires to adjust to the cobbles and tarmac.
I haven't googled it but ....