I know at least one adult who does. Her boyfriend bought it for her and it lives in her bed.
A sibling packed a teddy when going overseas to a military post.
I have a cute polar bear that I used to bring out of the closet at Christmas time. That is, until one of my kids swiped it!
My kids both swear they are going to take their softies to college with them. I'm not going to argue about it.
I can see how a stuffed animal could be a good prop for an adult who needs props in bed. The other night I was using my kid's stuffies as a prop as I helped her with her homework.