Because genetic monsters are supposed to be PG?
To me part of the idea behind the Hulk concept was that the Hulk was everything Banner wasn't. The Jekyl and Hyde scenario. Banner's a vegetarian, Hulk's a cannibal. Bruce lets anyone walk over him, Hulk bludgeon's to death anyone who he thinks is mocking him.
And really I always found a lot of the 616 Hulk stuff childish.