I don't get why people keep saying this. Phil said something to the effect that it was hard enough accurately emulating Power PC on a fixed set of specs of the Xbox One, yet alone trying to do it on PC with all it's different configurations.
Yes it is extremely difficult to do so, as it would have required the BC team to emulate or convert current PPC instructions to x86. They had a couple of different version of their Fission emulator, first time they pushed it out they emulated the entire dashboard, and wrapped the games in that, and they also had a functional converter for some games to directly go from PPC to x86. Before you say that's impossible it's very much already been done before and it's on GitHub. https://github.com/rexdex/recompiler
Sure the configurations of PC's matter, and that's why some emulators work better on AMD then Intel, and Nvidia to AMD and vice versa. It's just a lot of hotfixes to be done on many many different PC builds.
It's not something impossible. It just takes a lot of resources to do.
The one difference between MS doing this and someone doing it as a hobby? MS has all the resources to put people on it even for just maintenance, and to boot they also have the documentation for literally everything to do with the console. All of the instructions, and all the hidden things that most devs would not know about the system they have access to that information.