Originally Posted by ?uesto
Because the appearance of a drummer, (or a full band, for that matter), on stage looks much better than just one rapper. People also get to feel the drums when they get hit. You don't get the same effects by putting some speakers up on stage.
As for why they don't record with these drummers; it's more expensive and more time consuming than making a beat and looping it. Also, few drummers are capable of, or are willing to play the same beat for a rapper for 2, 3, 4, or 5 minutes per song.
My opninion, rap and hip-hop would be epic if they had live drummers for there tracks in studio. It would bring a whole new era of rap and hip-hop now, because they use a drum machine, or drum and beat loops with like Reason or Frooty Loops