If you're trying to have an archival format that pretty much any computer can open out of the box, zip is the only option. If you're restricting yourself to Linux computers specifically, there are definitely more options, but Windows can only handle zip files. For all other archival formats, the user has to track down a program which can handle them. No, that's not hard, but it _does_ raise the bar of entry somewhat, and there's really nothing wrong with using zip.
Only Linux and Mac users complain here about lack of 7z support in their oses.
