T-mobile will basically let you stream any music for free. Video they'll still punish you, but music appears subsidized by the vendors. I have a 64GB phone and had every plan to load it full of music, but I discovered that I have near-instant access to all 200-plus GB of my library whenever I need it. You get say, Netflix and Hulu in a pissing match and I'll bet you one or both of them ends up subsidizing the data on that, too. At that point it comes down to how many Youtube videos you can watch over LTE.
Damn that's not bad. Currently only Spark in NZ subsidizes data for music streaming, but they just pay your Spotify subscription for you. So we have a ways to go, but hopefully things will change in time. Netflix is only just taking off over here but it's definitely happening. The small time competition companies just in our country are at least making people aware of the services they could be having.
I suspect things will improve - not fast enough, and not with enough quality, but they'll improve. Cell phone contracts are pretty much pure margin; they're amortizing the build-out so it's not like they're getting free money but that amortization can be pushed out if it justifies more customers. Market forces in the US have made cell plans a lot less rapacious. I remember when plans came with different numbers of texts per month. Nowadays it's nearly impossible to buy a plan without free MMS.