Personally, I view my corporeal "avatar" as a rather annoying restraint (I have no physical disabilities, though I do suffer from arthritis).

A non-corporeal/virtual avatar can navigate spaces with ease- overcoming gravity (flight), obstructions (sit-on-a-prim-and-move or really fast flight), or even (through scripted assistance) being able to move from point a to point b without occupying the intervening space.

Though my views are brought about due to my arthritis, I suspect that most able-bodied people see a distinction due to taking their physical body for granted- it's always been there, and it's considerably more difficult to modify (tattoos are painful, a hair cut takes time to grow out, excess flab requires exercise or liposuction) than a virtual avatar (change skin, change hair, change shape)