> there's extremely rarely a reason to check the mirror on the side close to the rail.
...
You're literally responding to my post where I say this is not possible on my car. There's no orientation which doesn't leave a small blind spot. Not large enough for most cars, but definitely enough to hide a person/bike.
> The problem doesn't exist if people were just taught how to properly adjust their mirrors in the first place.
The problem being solved here is that, no matter how many mirrors of any configuration one has, they are still a squishy human who will eventually make a mistake, given that mirrors are used hundreds of times per driving trip. Or they bad-luck into a situation where another driver changes the situation faster than a reasonable, human mirror-checking regimen would reveal. These systems add a layer of safety for when, not if, that happens.