They aren't doing this for any benevolent reason like they are doing us favors, or because it's the wave of the future. They are doing it to look good in the face coming legislation that will do away with proprietary set top boxes. Cable companies make huge amounts of money on box rental fees. They aren't happy about the proposal, but AT&T is looking for a way to make us think they are the good guys and at the same time keep us from buying a 3rd party set top box.
https://consumerist.com/2016/09/27/advocates-lawmakers-even-best-buy-call-on-fcc-to-approve-cable-box-plan/Personally aside from losing DVR ability, I really like streaming. Time Warner/Spectrum has an excellent TV app that we use on a couple of ROKUs in the house instead of having a box. Now if Netflix can get contracts to open 100% of their content to streaming, I probably wouldn't need cable at all.
EDIT: wowens79 beat me to it!