a while ago I recall an erosion survey that concluded that in most cases bikes eroded the path no more than the same number of boots and shoes crossing the same point but there were some vagaries about the report. It certainly concluded horse wear was much much greater.
Our wonderful, and it is wonderful, mapping of footpaths and bridleways was done locally back in the day before mountain bikes and it certainly lacked joined up co-ordination, hence one person classifying a trail as a path and another a bridleway, often where a person surveyed ended at a county border where another person surveyed it from the other side, sometimes giving a different result. I also suspect some local 'persuasion' was used by land owners wanting, or not wanting, a path to be classified by actually what it was used for. Lots of the lead mining Pennines trails stop half way, its crazy to think the pones stopped mid trail and turned around. Or that coffin ponies taking a corpse to a cemetery would similarly stop. but it is what it is.
I have used footpaths and in more urban areas nobody really seems bothered but out on the hills its more get orf myyy lannnddd. When I have, I have always shown respect to people I meet been friendly and walked if I feel its needed. I used to ride up to the top of killhope law on a footpath a lot, all of it was a 4x4 type track till the quarter miles of moorland, it made a great loop and didn't make the trail worse.
So, yes I have but with care and respect. SKiddies are for kiddies.