Why isn't voting mandatory, just like taxes?

On your 18th birthday you would turn in your permanent voter registration card along with your draft card. I'm tired of meeting smart people who don't bother to vote. And it's pretty clear that registering and voting is currently too difficult for about 50% of adults age 18-34.

"Oh, that would cost a fortune" you say. No problem. Just fine the lazy bastards who still don't vote in the mandatory election to pay for the new process. Pow! I fixed America.