Tar files also have the miserable limitation of having no index; this means that to extract an individual file requires scanning through the entire archive until you find it, and then continuing to scan through the rest of the archive because a tar file can have the same file path added multiple times.
That makes them useful for transferring an entire set of files that someone will want all or none of, e.g. source code, but terrible for a set of files that someone might want to access arbitrary files from.
Some things are used for interoperability, and switching to a newer incompatible thing loses all of its value.