For me personally, I wouldn't ask my wife to "pity fuck" anyone including myself. If she isn't into it I have no desire.
If I thought a gal was offering me a "pity fuck" first of all I'd turn her down flat. If I didn't turn her down and decided I was going to take her up on it, well you've heard of inverted nipples, I'd have an inverted penis. Talk about can't rise to the occasion, mine practically crawls up inside me if things ain't clicking.
It's just the way I tick, but in 38 years I've never seen a woman I'd beg to fuck. OK one in 38 years, and I married her.
just my 02 cents
-D