What's so bad about a 2 year contract?

OK so I Really want an iPhone 4s and yea I know about the iPhone 5's and i'm not interested in that. But my dad won't let me get it because of the 2 year contract and yea i know spring offers prepaid iPhone 4s's but my dad wouldn't pay like 600 dollars for that. And the 2 year contract one is like only 99 dollars so i don't see why that's so bad. I know you have to pay like 50-80 dollars a month but if you talk, text and all that stuff a lot wouldn't it become less expensive rather than to keep on refilling it? So what's so bad about a 2 year contract?

Added (1). Sorry i meant Sprint.

Added (2). Please give me real answers

Better than a three year contract am I right

It's a long term commitment you're forcing yourself to commit to paying a lot of money, every month for two years.especially not great if your job security's not great

I think it might be the data plan, not the contract. And I think the service plan is better than just buying the iPhone. And you still pay as you go for the iPhone w/out the 2-year service plan.

Your stuck paying 2 years for the same phone. Some people don't know if they will even be able to pay because financial issues that can come along.

Right now I'm stuck because I want to purchase iPhone 5, but my contract with iPhone 4 is for another year. I have to pay full price for the phone if I want it.