What about if you spend most of your time tooling around on bike paths, where you're never really near cars nor really riding off road? Maybe that's a reasonable place to consider not wearing a helmet, though running head on into a baby stroller could still cause some damage.
Was on a bike/ped rail trail last fall and had 3 deer come down onto the path from a 8' high bank, I had to stop on a dime to stop from hitting them or them hitting me. I went head first over the handle bars and head and shoulder hit first. I was glad I had a helmet on! You never know... Average speeds are higher on an ebike, you must take that into account. Rarely is there anyone around early in the morning when I ride. Had I not been wearing a helmet that morning I could have been laying there for some time. I don't know how much a bike helmet would help if hit by a car at speed, but I know how much a helmet helped me in a single vehicle accident. Only had a sore shoulder and a headache.What about if you spend most of your time tooling around on bike paths, where you're never really near cars nor really riding off road? Maybe that's a reasonable place to consider not wearing a helmet, though running head on into a baby stroller could still cause some damage.
We don't have dedicated bike paths, they are multi-use paths and pedestrians tend to take up the middle, wear headphones blasting music, and then not hear what's around them. I've come close to having accidents on these paths a few times because I had to suddenly stop due to someone else's actions. I don't see the need to not wear a helmet especially when my helmet is comfortable.
Again, what is the benefit of not wearing a bike helmet? Am I somehow safer? Is my head better protected without one? If I fall will my injuries be worse because of a helmet? Other than "cause I don't feel like it" what are valid reasons and benefits of no helmet?
I can see that I might be injured anyway and the helmet may not prevent all head injuries, but worse?
Answers to some of your questions:
As far as near-accidents with pedestrians, I hold the bicyclist responsible 100 percent of the time. I nearly come to a complete stop when going by pedestrians and always speak to them.
I just don't think cyclists have any responsibility to slow down to a crawl when they're on a path meant for them.
Note: you stated "multi-use path" but then seemed to discuss divisions of the path. Where I live a multi-use path is just a plain path, there are no markings for bikes here and pedestrians there.
If you're talking about a bike lane on the street then I agree the pedestrian has a higher level of responsibility, but even in that case the bicyclist must be safe and prudent and make every effort to avoid hitting a pedestrian, morally and by law.
I spend half of my commute riding on a multi-use path called Chandler Bike Path in which roughly half is designated for pedestrians, and then the other half is for cyclists and has a clear white dividing line that separates it from the pedestrian area, and also a dashed-yellow painted dividing line to serve as a was to separate bicycle traffic going in either direction. On my commute, I usually encounter anywhere from 10 to 100 pedestrians on the multi-use path, and 90% of them stay within the pedestrian area, but often there are runners who need to pass slow-walking pedestrians, and they do so by darting out into the bicycle path without looking to see if there are any cyclists. Some of them have given up on staying within the pedestrian area because they have to leave it so often to pass walkers, so they straddle the line between the pedestrian area and the bike path. There are also groups of moms with strollers who walk three-abreast, and one of the moms is always walking in the bike lane, oblivious to the dangers and the presence of fast-moving cyclists. Also, small children who aren't properly supervised by their parents tend to dart out on to the bike path. I try to slow to 15 mph when passing pedestrians so that I can more easily swerve or brake if they dart out in front of me. I think the better solution, though, would be to have separate paved paths for pedestrians and cyclists, and to have them clearly marked as such, and also to have fines for violators posted on signs every block or so (though I imagine you wouldn't need any enforcement of these rules if the rules were posted often enough and if the paths were painted so as to make it clear which groups could use the paths).
I've found that on Strava, cyclists seem to universally hate this bike path so much that they've nicknamed sections of it "Chandler Moron Bike Path". I assume that their disdain for the path has to do with the trouble they've had on the path, whether that came as a result of strange interactions with slow/inexperienced cyclists or with pedestrians who darted out in front of them or blocked their path.