No company really cares about its customers, it cares about its bottom line. A company will gladly lose a customer that is costing them money with a grandfathered plan that is way cheaper than what current customers are paying. A $5 increase is still way cheaper if you use a lot of data.
Data usage has increased tremedously from the beginnings of the unlimited data. If the companies has seen how dramatically data usage would increase with the advent of the smartphone, they would have never offered unlimited data.