alt Hacker News> […] this is by design of both companies.
This is more of a fundamental technical limitation of operating systems and networks; I don't think it is possible to design distributed communication between arbitrary service provider infrastructure and end-user devices without an always-online intermediary reachable from anywhere (a bouncer, in IRC terms) that accepts messages for non-present consumers.
Yes, however the fact that it is not customizable is what is annoying, you are forced to rely only on the OS makers' implementations, which I guess should be expected in the day and age.