Different cash cows at different times. First it was minutes, then messaging, now it's data. They offer unlimited minutes likely because even if they offered unlimited talk, most folks would only actually use less than 1000 minutes a month. Data is their current cash cow. Would data buckets increase? Eventually. AT&T and Verizon haven't yet felt the need to be more competitive in terms of pricing as they don't have a lot of competitors. However, it looks like T-Mobile's new "Un-Carrier" approach will shake things up.