More solder joints? More radio interferience? Less flexibility in the wires going to the motor? Less spectacular looking? Maybe that's why.
It's not rocket science to prevent a short and the anodizing of the heatsink is not even electrically conductive. Patrick @ Castle creations insists that the bullets touching the heatsink is not a problem and never was.
Check out my custom converted 8ight:
Sub 7lb, lowest CG of any 1/8 buggy