I was thinking the same thing. Everyone jumps to a conspiracy. As someone who works for a software company, if it makes the company money, it will get fixed.
Bugs happen all the time, the more serious ones affect a larger population and suddenly its a conspiracy or money grab. There is no such thing as a bug free software program designed by humans, at least not in my experience. I think it is important to report these things and it's unfortunate that it has taken so long for them to resolve the issue. I know I haven't purchased any music experiencing the issue because I preview all music I purchase because I'm a music snob. lol
I don't buy albums just because it is an artist I like. I don't even buy albums when it would be less expensive to buy the album instead of all the songs I like from the album. That doesn't happen often but it does happen.
My point here is that if I can't preview a song, then I don't buy the song. I find it highly unlikely that they would purposely engineer a bug to disable the preview button only on certain selections of songs to attempt to herd people to their streaming service. That makes no sense at all. Its Apple, if they don't want it, then they just stop doing it. I've not known them to be coy about their decisions.
THey just designed an iPhone frame out of titanium. Why? Because they wanted to. It is way more difficult to work with than aluminium.
Its a bug, plain and simple.