But if no-one gives you a chance to try them?
OK, let's extend the logic here. If no streaming company is willing to offer the alternatives maybe people could do their own DIY tests and try the alternatives. Neither bitstacking nor noise shaping down to 16bit require any change to the player software or hardware. So if programs can be used by people to generate bitfrozen or noise shaped versions, people can use them on some of their existing high-rate 24bit files and judge for themselves.
The can also FLAC the results to assess the effect on the required file sizes and stream rates.
I've already made available demo programs for the above. Anyone interested in making such use of them? I can do various things here, but it is clearly a matter for others to decide if they, individually, can hear the relative quality in a controlled test.