I check for credits of my models because I like to see how they are used in people's art.  In fact thats one of the things I really like about 3d modeling:  my oil paintings hang on someone's walls and after the sale I don't get to see them, but 3d art gets new perspective from lots of other artists.  I like to see the things I work so much on as others imagine them too.  Plus, as I see how folks use the models I can tailor new ones to suit.