I don't know about elsewhere but locally (& beyond) I've found very few reasonably broad footpaths that don't have recent mountain bike tyre tracks. I must admit that I have become more "flexible" in my old age & will use decent tracks without gates or stiles that aren't bridleways. On occasion I'll even lift my bike over a gate.
There is a footpath I used to use when I first started riding an MTB in the 1980s when I thought less about the designation of the path & whether I was "allowed" to ride on it. It is an old miners track on the east side of Winter Hill.
I eventually decided to largely avoid riding on footpaths.
Looking at Strava segments recently I noticed that there are 4000 people recorded as riding down that path & 2000 recorded as riding up. A quick look through some of the data shows rides going back to at least 2012.

- Going down

- Going up
There are other segments locally on public footpath routes also with 1000+ records.
It does rather make a mockery of the distinction between footpaths & other rights of way with regards to riding a bike on them.
Former member of the Cult of the Polystyrene Head Carbuncle.