[MereInterest]

Because even determining that there is an update available requires checking against an outside source to see if an update is available. This requires internet access, which requires handling network protocols, network security and encryption, none of which have anything to do with file compression. Increasing the scope of a project introduces additional failure modes, and a larger security risk.

If a project already performs telemetry, or if they have developer announcements, then the project has already increased its scope, and checking for updates is a relatively minor addition. If it is a well-behaved stand-alone application that doesn't make unwarranted external connections, then checking for updates is a large increase of scope.