This is my husband's experience. I was healthy when we married. First came Bell's Palsy, then failed back surgery which has crippled me for 12 years, then a stroke last year. I keep losing ground but never give up.
He's 10 years younger than me and at one point I told him I'd understand if he needed to find someone closer to his age, not saddled with physical problems. He reminded me he'd done the, for better or for worse, in sickness and in health, and he meant to keep those vows. Love that man
I know this is the opposite direction of the OP, but sometimes partners do bail because they can't cope. These would be the people that automatically look away from the disabled.