There's also the issue of dependencies on other non-default packages. Do you ask the user to install another repository? Do you host your own repository and distribute the dependent packages in it along with yours? (Note this is much more complex than building and hosting a single .deb/.rpm)
Not to mention "desktop Linux" is not a thing. Supporting Fedora, Ubuntu and opensuse, for example, are all distinct efforts with only minimal overlap in terms of effort (think not just initial dev, but ongoing maintenance and testing).