As you mentioned, reducing the costs usually amounts to taking something out: this can piss off users, particularly if they were not informed and no discussion took place. An example that comes to mind was the decision by Mozilla to stop supporting the ALSA driver in Firefox based on the telemetry showing little usage.
Ths example also shows that often data are biased and making a decision solely based on data is not ideal: ALSA is (was) the default choice on most GNU/Linux and BSD distributions, where firefox is usually built and distributed by the maintainers with telemetry disabled.
> is akin to demanding free beer that people can optionally pay for.
This is similar to how donations work: with donations you can't force people to give you money but you can be very insistent and it can leave users with a bad taste in their mouth. Also, if you are implying the service providers are entitled to collect all the data they can, I think this must have limitations. Running code on the client side from which the provider only can (directly) benefit should require permission, because you grant users access to server and so should the users grant you access to their machine.