Why not just issue a warrant to drill a hole for a camera, or use other tech to passively see through walls?
Guess that takes away the fun of brute force entry and trigger happy law enforcement that needs to put their training to use.
Civil forfeiture is another huge reason. Not about killing them, but taking their property.
https://www.youtube.com/watch?v=COa2t_m1K7I for those who aren't adverse to Google's tentacles.