I am living in a region (european Alps) with lot of tourists, lot of trails and nearly 80% of all bikers are e-bikers. On Sundays when the sun is out that number goes up to 90%.
These bikes are perfect for commuting to work. Or older people being still able to ride. Or disabled people that would never go up a hill without an e-bike. I do know old people riding e-bikes and I do know disabled people riding e-bikes. And at least here in europe the big amount of e-bikers are just older people. Most of them are not wearing helmets, they just cruise around on weekends. It looks weird because someone sold them a Haibike with 6" of travel and fatbiketires on.
I never met a single e-biker on a real singletrail.
But lets face it: a lot of trails are currently forbidden because of the growing number of e-bikers. In this area there are 80 new "cycling forbidden" signs where not many people were riding in the past. Now in the time of e-bikes it has become too much for the land owners and farmers in that region. And of course it is now forbidden for all bikers.
Personally I don't think that a bike with an engine belongs in the nature. We have areas for that kind of "sports" (skiing areas, gondolas, bike parks, motocross tracks,...). Sadly I don't think someone could stop that kind of innovation. There are already patents on motorized skis, so you don't have to walk up.