Why do I have to buy a data plan when buying a Iphone 4s from the apple store online?

I'm buying a Verizon Iphone from the Apple store but why do I have to purchase a data plan right now? I planned on waiting until next month and just taking it to a store to get activated. Or is that not possible and i would just have to buy a unlocked phone?

The iPhone is a multimedia device that is preloaded with numerous applications. Many of these applications and those you opt to download on the device require a data connection. The cost of a data plan can eventually add up if you are not careful. If you want to avoid overage charges on data or you simply do not have a need for the data on the phone, you can disable the data plan on the iPhone at anytime from the handset.