Problem: My provider does not allow one to activate a smartphone without paying for the data plan.
I don't have a smart phone myself, but I work at a telecom, so I asked around. I couldn't confirm this officially, but it was suggested one reason for requiring a data plan is because US carriers can't stop you from using certain smart phone features, whether or not you have a data plan.
We tend to assume that telecom carriers are like our cable company - we select a cable package, the company flips a few switches, and voila, we only get the channels we pay for (usually

).
US telecoms, however, are a disorganized lot. You have your wireless carriers, with cell towers, but usually using wireline backbones to connect the towers to their networks. You have LEC's (Local Exchange Carriers) who are allowed to bill other carriers access charges to connect calls to/from the carriers' networks, tandem operators who carry traffic, VOIP (for which no one seems to know what the rules are), and so on. And now we have all sorts of cool data offerings, most of which were tacked onto the existing infrastructure.
Just blocking calls to/from a number, or canceling the long distance carrier for a customer can be a nightmare, involving not just the customer's carrier, but a LEC or other carrier. And if anyone in that chain drops the ball...
This is what we get for having a single phone company, split into multiple companies, with other entities, some of which have merged back together, with various charges allowed/not allowed between the parties, tacking on wireless, number portability, VOIP, and the kitchen sink. Basically, all of US telecommunications is one big kludge, regardless of which carrier you choose.