Gravescratch didn’t particularly want to go to the trouble of walking smoothly enough to not jangle the bell, and he certainly can’t be expected to spend the day with a noise-making object near his audials. What else is he supposed to do with a bell? Besides, it probably tasted good.

And I don’t think he’s ever vored anybody. He isn’t large enough to swallow most sapient beings whole, he makes a point of never swallowing things alive because that would be cruel and potentially dangerous, and he doesn’t kill sapient beings for food. 

(Now, if someone is dead for other reasons, he’ll certainly eat them, but that’s a different thing entirely than vore.)