system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] Why doesn't the Red Hulk have a mustache?

Thaddeus Ross has a big white mustache.  However, when he transforms into the Red Hulk, the mustache disappears.  How do we explain this?  Shouldn't the Red Hulk have a mustache?
gpt
One theory is that the red hulk, like the green hulk, is a completely separate body from the host. This means any similarities between the two bodies is purely coincidence and not telling of how either the host or the hulk will or should look.

So basically he looks different because he is different.

Edit: the theory is further supported by Thaddeus' head hair being gray, while Red Hulk's is black.