Tell that to Merced Melchor-Meceno. Who gets deported twice, and when he's caught a third time, he gets sentenced to 75 months in prison. A sentenced affirmed by the Ninth Circuit.
It's true that we don't throw you in prison the first time you come over. (Though we do "detain" you in prison if you can't make bail and don't agree to be immediately sent back.) But it's not at all true that you can come into the U.S. as many times as you want without consequence. Especially if you've previously been convicted of a crime.