Given that the goal of the Pi is educational in nature, think of it as an experimental platform with many names and potential uses, only one of which is "Baby's First Media Center/Centre" that kids of all ages can use to learn how network-distributed digital video and audio work.
Beyond the previously-mentioned limitations, the biggest problem with digital media streaming is network contention, both internal to your location if you have multiple people each trying to stream GBs worth of content at the same time, and upstream on your neighborhood's and intermediate wide-area networks. Network performance can vary widely depending on the time of day, and problems ascribed to streaming services (beyond lack of support/compatibility) can actually be caused by the network. Even the Pi can outpace network capacity without really trying hard in many places, especially if you're not located in proximity to wide-area network capacity (fiber optic trunks).
If you really understood how the technology works, you'd be amazed that any of it ever works at all, let alone as well as it does. Murphy (of his renowned Law) hasn't retired, but we seem to gradually be making progress faster than he can muck around with our stuff. Even 10 years ago, no one was predicting a $35 credit-card size, open-source, user-programmable computer capable of 24 billion floating-point operations per second and 1080p digital video output, that consumed at most a few watts of power, and now there are nearly a million of them in the wild. That it allows me to play all of my music (via Aqualung) and stream 1080p video from local storage (via VLC), in addition to developing 3-D STEM educational software, is nothing short of astonishing compared with my early computing experience just a couple of decades ago.
I have to laugh when I hear people complaining about their cell phone dropping a call, an aircraft arriving a few hours late, or not being able to stream any movie they want, whenever they want, with no glitches. They have no idea how good life is for them compared to that of people in many other places, and that they're able to routinely do things that not even the richest people in the world could do less than 30 years ago, for a pittance.
The best things in life aren't things ... but, a Pi comes pretty darned close!
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!