the assumption that all of those several million
people will want to print from anything with a CPU ("whatever computing
devices one uses") or that that is even the common case.
There's been no assumption that "all" want any-one-thing.
As for common, print-from-any-device-you-use is common here, with ~ 1K 'in-house' users, and easily-dozens-per-day of 'guests'.
That's FAR more common than your 'objection' to it.
As has been said repeatedly here -- paraphrasing, "different strokes for different folks".
If the developers think its important to support their user-base, what are you objecting to?