I'm not defending them, just saying that it's foolish for an enduser to expect anything different when they already don't pay musicians and that is the primary content on their platform.
I can pretty much guarantee the average user would complain way more about the quality of simple TTS than they would the time limit. It would likely be a much bigger PR issue for them. AI generated TTS would probably be good enough for most but that is just another cost.
Regardless, the licensing involved with book publishers wouldn't allow them to just produce their own audiobooks like that. So it is not really as simple as "just a choice".