Many young Basketball players ask this question (I even asked this question when I was young). Basketball is a running game, there should be no time while the basketball is in play that you're not moving and because of this you could end up running, jumping and communicating for 3 or maybe more minutes at a time. 

Answer:

Your coach makes you run because: 
  • Make you run faster than your opponent
  • Make you able to run the whole game (can you play a whole game at 100%?)
  • Make you jump higher so you can get rebounds 
Also lets not forget, if your talking while the coach is talking, you will probably gong to run, and run lots.

Coaches are not out to kill you with running, your coach is there to make you a better player. This will help him and the team win more games and help you improve.