Speaking of wasting time, this entire competition is a huge waste of time. Think about all the time put into artwork that never makes it onto a shirt. (Although I hope people find a way to recycle their work.) Everyone is just doing it for fun since they have to know that the chances of 'winning' are /very/ small.
It's sad that you see it like this. It's not a waste of time for people who want to practice their art and challenge themselves creatively to come up with a design that is both interesting and follows the guidelines.
And yes, the chances of printing are small for some, but many people work really hard and wind up getting printed eventually. If nothing else, they can get feedback on their work from shirt fans and artists alike.