Cause .tar.gz is not an executable binary in itself. It is more like a zip of the binary and its support files. Since it would be really difficult to distribute and maintain native binaries for every type of distro, application publishers used to just distribute for distros that has a larger userbase, like a .deb for Debian/Ubuntu and a .rpm for Fedora/RHEL/Suse, and then they would provide a tarball for any other distro. Flatpak and Snap have been introduced to eliminate this overhead from application developers, but they still offer tarballs as the newer solutions are still far from standardization.

For an example, Mozilla being forced to use Google Location Services as default even though Mozilla has its own. I am also a Firefox user but it always makes me wonder what other TnCs forced on Mozilla as part of the search deal.

For learning system administration, I think Cent OS Stream can be a great choice. Not because it offers something special than others but because it would familiarize you with the RHEL/Fedora family and in my experience majority of enterprise-servers are using one of its family members, be it RHEL, the former CentOS, Oracle Linux, Amazon Linux or some other variant.