I may be completly wrong here but a couple reasons:
1) If you mess up, you crash the game
2) 3D rendering requires hooking DX
3) Larger footprint to mess up and get banned
4) In-game user interfaces vs dedicated frameworks (like WPF, Qt, etc.)
All in all I'd rather write a good caching system than have to worry about the extra protections I'd have to implement.
Could you please elaborate on what you mean by "chicken"?
P.S. I'm strictly talking bots here (DPS bots, fishing bots, AH bots, gathering bots, etc.) Not hacks (wall hacks, fly hacks, etc.)