There are a lot of people on this forum convinced they can tell the difference between 256kbps and 320kbps and I'm not so sure about that. iTunes has been based on 256kbps for over five years now, I think. I don't understand why it would only be annoying certain people now, with the introduction of Apple Music.
And surely while on a cellular connection, if your connection dips slightly, you would rather the quality dipped for a few seconds, rather than a complete pause and buffer?
And certainly, the deal between Apple and the record industry for a streaming service, like Apple Music, is different from that in place for the iTunes Store. Just as Netflix has a different arrangement to Amazon, for the streaming/sale of movies, respectively.