There are some Mexican traditions that I may never fully understand but as long as I'm here, I should try to embrace them. This is one of those traditions.
I've often thought the idea of a piñata is odd seeing as how we give our kids their favorite character & tell them to beat the crap out of it for candy. But it is a traditional birthday celebration here in Mexico just like "mordida" so I will continue to participate. Plus, who doesn't love the lesson that you have to work hard for your candy.
Ps, mordida translates to "bite it" in Spanish.