The Linux distros have all kinds of system notification mechanisms. Some are better than others, but for the most part they function the way they should. On the other hand, some developers, like those from the elementary OS team, go a little bit further and are able to provide a much better experience for end users.
"System notifications" is the kind of feature on Linux that is usually taken for granted. It's been available for a long time and users are now ignoring it completely. It's there and it does its job, although it's implemented differently on various operating systems. Some operating systems do it better than others, but it's rarely noticed.