There aren't many places hiring uncertified techs in AZ, because they want to spend their limited man hours on certified techs. In many places, anecdotal evidence shows you can't even volunteer in a pharmacy without a license (although I don't know if certification is implied). So, I guess the short answer would be - to gain experience in the field (ECs, friend).
While we're talking about jobs - uncertified techs in AZ make significantly less in most cases I've run across than certified techs. If you need to work while you're in school, being a pharm tech is much better than a lot of entry level positions. In AZ, you can be a tech without a certification for 2 years only - what if you need to work during school & need a 4 year to get into your school of choice? The smart move, in my opinion, is definitely to become certified early, so the ROI is higher.
Both of these points ignore the fact that it looks good on your pharmacy school application to be a certified tech - it shows you've at least taken some steps towards the pharmacy field as a whole, rather than being just a kid building castles in the sky. Also, any experience you actually get in a pharmacy counts as a good EC. While neither of these things will necessarily "break" your application, they may "make" it when an adcom is deciding between your marginal application & someone else's.