It may simply not be a disability in their eyes. If you can use magic your ability isn't as grounded in your own physical ability. A fighter sure, but there are other classes that may not have a desire to "fix" what we would consider to be disabling!

This would almost certainly be similar to how people on the autism spectrum feel vs how people who don't, expect them to feel.

This is where a good storyteller would have a blast.

Maybe a mage could heal it, but then they would take on the disability themselves.

Or a magical disability is the result of a 1:1 battle with another magic wielder. Only a being of equal power can cause permanent damage.

The disability is a payment for some rare power. Maybe you lose your eyes but can now see the astral plane and pilot the Event Horizon.

Along with what everyone else said - in some universes using magic has a cost to the user. So one could be exhausted just getting around by constantly needing to be floated along.

We have it set up in our campaign where it's often seen as hella rare for someone with that level of magic

More specifically out campaign turned into a space campaign amount lv 15 cause our planet exploded cause lore lmao

But there's like planets where there's nothing but the most basic of cantrips so we end up being gods to them

so far only one has attempted to exploit this and it was the cleric lmao Mainly because they are now the last embodiment of their God and are sort of designed to become them or something lol

why would there be a magic character who relies on a real-world wheelchair when they presumably have magical abilities that would eliminate their disability,

Even moreso in something like a typical medium-high magic D&D setting, where most medium size towns have at least one person around that can fix those sorts of problems for people several times a day.

and why would that be someone's fantasy?

Because to some people the most important thing of all is representation of specific groups and everything else is secondary.