Why should you play with very little pressure?

I guess maybe so your teeth don`t hurt when you try to hit a high note and smashing your lips against the mouthpiece gives you that annoying ring around your lips... I wonder if t-bone does make you a good kisser?

The reason is that if you put pressure against the mouthpiece, you have to work harder for your lips to vibrate. In order to have a good sound, you want your lips to vibrate freely. This is why you should use as little pressure as possible.