I'll answer the question of why one picks one choice over another. Was a mess of off-topic posts here, but I see they got moderated. In short, it's about selecting the right tool for the job.
- What's the job? Getting yourself out of your seat, behind your screen, and onto the trail? To test something in a specific type of environment? Explore places where bigger and heavier vehicles can't go?
- Is there some goal or ideal result(s) that you'd like to achieve? Go further, faster, and higher in a certain amount of time? Observe the world and how it's changed? Feel good about yourself? Reshape your body?
- Are there any limitations or important considerations? Your fitness? Trail rules? The trail technicality itself? Traffic? Safety, risk, and/or responsibility? Time? Support/supply line robustness (friends, community, emergency contact)?
- What tools are there? Walking/hiking? Running? Driving/shuttling as far as you can past the undesirable stuff and finishing the more desirable with manual labor? Bikes (road, cx, hybrid, cruiser, mtb, etc.)? Other wheeled vehicles: unicycle, recumbent, off-road skateboards and roller skates, wheelchairs, trikes, quads (non-motorized)? Powered versions of all of the wheeled vehicles? Higher powered motorized versions?
Why do people pick mtb and shuttling over other options? They likely chose it to address the earlier 3 questions better. I chose e1mtb to ditch shuttling, including shuttling to the trailhead from my house, and to ditch weight weenie upgraditis. I still look to fulfil the jobs and goals I had when I was riding a normal mtb, yet fit within more limitations. I still have a normal mtb due to those increased limitations (legal issues), but without them, I feel like I could possibly get away with it being my own bike. What I spent on my e1mtb is 35% less than what I spent on my last regular mtb, a Yeti SB5c customized with carbon wheels and other carbon goodies.
This is just a case of evolution and adaptation. Mtb has long been moving away from weight weenie dirt roadie style riding. Electrification is rapidly maturing. It's only natural that this sort of morphology/phylogeny happens. People take two or more good things, combine them, and, viola, create something new.
It's just a new option. It doesn't replace others. Lightbulbs haven't totally replaced candles, oil/kerosene lamps, and torches. Cars and motorcycles haven't replaced bicycles. Elevators and escalators haven't replaced stairs. People used to buy huge toolboxes, filling them with tools with individual handles, but different sized/shaped heads, from screwdrivers to spanners, until someone thought of a way to use the same handle and just swap the head. Now you have crowfoot and screwdriver bit attachments. You have SUVs and wagons, Porsche 911 and Ariel Atom; different options that could serve the same job, but have differences that meet specific needs better. 26" is still around, despite the wave of 27.5" influence encouraging makers divest in 26", since there are still a market of people looking to ride bikes who are under 5' tall, namely children. They might want a capable bike too, perhaps to hang with their dads, maybe one with pedal assist to aid in that goal.
The only issue I see is presumptuous judgment. People are narrowing their tolerance based on semantics of terms like motorized, and how they happen to judge "motorized". Debates surrounding semantics and categorizations have always highlighted one flaw: giving simple definitions to stuff is virtually the definition of being narrow-minded. Ironically, in order to try and simply communications, narrow-minded scholars created new terms to define things that were seen as distinct, to combat how words were having their meanings stretched. It's up to the masses to use them though. Who uses the term ultracrepidarian anymore? People these days just use rude, idiot, or maybe even troll, for anyone they find to be disagreeable to their standards. How many end up being unable to figure out why they're called such, and end up questioning that, rather than continue with the original topic? Even celebrated philosophers can succumb to the flaws of such behavior--Plato was applauded for his definition of man as a featherless biped, so Diogenes the Cynic plucked the feathers from a cock, brought it to Plato's school, and said, "Here is Plato's man." Do you feel like you got your veggies servings if you drank tomato juice, or had peppers, okra, cucumber, pumpkin/squash, or avocado? Was getting your veggies really the point of eating/drinking them, or were you after specific nutritional health benefit, like lycopene and because one or more of them pleased your tastes/tolerance more than other options?
I'm clearly pointing out the different weight and power classes here. There was a gap between moto and bicycle that's getting filled out here. It's interesting to me, since I worry about how legal my e1mtb is, and I was curious what moto trails look like and how they ride on an ebike. If they're not fun on a mtb, but look to be fun on a proper MX bike, and I can afford one, then why not? It'll be a new goal of checking out the MX side of things, since I'm admittedly ignorant about it. That means I'm unfamiliar with maintenance regarding their combustion engines. Right now, the reasons for why not is that I don't know where the welcoming trails or people are. All I know of are the MX tracks, where'd I'd be trying to hit doubles and triples. I haven't even tried a BMX track. Might be worth a look to expand my world. Trying to avoid the presumptuous judgment that all MX trails are all loose with deep grooves, prone to poor drainage, and get branched out more and more after each rainfall, and won't be fun on an ebike. Might make me more level headed when I talk to the troublemakers on mtb trails, since I'll be asking them where the good MX trails are. xD