Dear Waddle Waddle,
By asking why Headcrab can't be more like Gish, you were implying that you think Headcrab should be more like Gish. Aka a Gish Clone.
Eat ass excretions and Die.
Wow, I'm sensing some hostility.
Okay, here's my solution. Just throwing this out there. Why doesn't everyone who doesn't like how Headcrab functions not play Headcrab, and everyone who does can?
The only thing I'd like to change about the crab is a way to alter the annoying death noise.