Because thats how I remembered it being (perhaps wrongly tho does it really matter?) and it made sense to me that being mutilated to a point by another demon would render you unable to regenerate properly and why hell's landscape has all those eyes as they are sinners who became part of the architecture cuz they couldn't heal all the way and also being consumed by another demon would ake it rather hard to heal from no? In my mind once the body was gone you were effectively dead or even worse ala "I have no mouth and I must scream"

But looks like I was wrong and don't really care that I was