I don't have a good understanding of the relationship between the content providers and the music services. Perhaps they have stored a version of the recording at a higher bit rate (pre-dithering), and simply provide that to the music services. In this case, all the other work done during the mastering process (including DRC tailored to lower fidelity playback devices and noisier listening environments) will be retained.
I was not necessarily suggesting that the music services do their own mastering, as this would require access to the pre-mastered version of the recording. I guess that they could pay for such access, and pay a mastering engineer to produce an audiophile version, or more likely just pay the content owner to do the same. Either way, it seems to me that for the music services to offer truly higher quality recordings - rather than just higher bit rate recordings - this work (and expense) would be required.
I guess I am just beginning to appreciate the fact that the "high-res" (ie higher bit rate) content from the music services is not necessarily any better sounding than CD. Technically, the higher bit rates should have better extension and quality in the higher frequencies and a wider dynamic range...but over-use of DRC probably negates any benefit of wider dynamic range.
Perhaps the real advantages of the high-res music services - at least for content that is not remastered - are simply 1) CD quality (lossless vs lossy), 2) convenience, and 3) access to huge libraries. I had hope for better sounding recordings as well, but it may be that there is just not enough of a market to support the expense of remastering for audiophile users.
IME they are getting better. Of course this is all subjective to my likes (we all have them) but I rarely liked any of the "new" Hi-res remasters over the "originals" when they started coming out. For me they seem to be getting better, I am finding more that I like over the originals than before. Could just be that I am listening to them more often now with a decent streaming front end... whos knows
All I know is for me I can always find a version that sounds good (enough) but I can also get past production problems and I know many cannot.