The problem with the D&D "Combat Wheelchair" isn't that it's "unrealistic" (at least not in ren-faire fantasy like the Forgotten Realms), it's that it isn't really about ttrpg play at all.
Like most things, it's what you make with it rather than the motives of other people for being interested in the topic to begin with.
To me, wheelchairs in D&D is just an opportunity to get creative with a new concept.
It am thinking up spells that spellcasters would research to help a wheelchair get over difficult terrain, or lower it's weight so it can be more easily hoisted up a rope. I am imagining things a combat wheelchair with magic and machinery added to it might be able to do. I am imagining other magical and mundane modifications which could happen for other physical disabilities, like blindness or a missing limb. I am thinking if this kind of stuff can better allow for long-term injury to PCs due to incurable magical damage. I am imagining what kind of magical damage would be incurable such as curses, partial disintegration, disease, anti-magic attacks, etc.. I am considering if birth defects would "heal" only back to what they were originally, making healing spells ineffective for that kind of disability. I am going down all sorts of avenues of creation for this concept which I hadn't before.
You can dwell on the negative, you can fret over the motivations of other people who you will never know and never encounter at a game table. Or, you can focus on the cool stuff you can make with it. I'd rather do the later.