I think just the belief we (hopefully) won't be aware of it because we'll (hopefully) be dead. Lots of people also choose to CTB where family members or friends won't find them- to spare them that. Plus I guess, death in general isn't exactly attractive. One day regardless, we'll all be corpses. And the method too. Some are more gruesome than others.
I used to feel quite worried about how my corpse might look for the poor sods who have to deal with it but ultimately, they must be used to it. Plus, there are things we can do to make the clean up easier. Lay down think plastic. Wear an adult diaper.