While it might burst some bubbles, do realize that every corporation that is in the media business is in it for the money, specifically profiting from it.
Of course, they are smart people and realize that if they only offered Internet access as a stand-alone product, they would severely (but not completely) eat into their other businesses, and if that were to occur, advertisers would begin having second thoughts as with whom they'd spend their money.
Yes. Data caps are neither a congestion nor an engineering issue; it's a business issue, pure and simple. And, frankly, if you're using their infrastructure to enjoy your service, they have every right to manage that content stream however they see fit. They also know that since everyone's doing it, you can't simply walk away (unless you're willing to forego service), and since the barriers to entry are so high, it would be extremely cost-prohibitive for you to go start your own company.
I enjoy my DirecTV service and will continue to do so until I can find a cheaper way to get my programming (which might occur sooner than later, and with the alleged DirecTV Now, et al. coming down the pike, DirecTV knows they can't forever raise prices on packages), and the same with my AT&T wireless. That doesn't mean I won't gripe (and have) about how AT&T won't allow you to use their unlimited data without also giving up my personal hotspot functionality on your iPhone (which is great for occasional kid usage).