Tar doesn't use any sort of index like zip does, so to extract the specified file the server side would need to parse through possibly the entire file just to see if the requested file is there, and then start streaming it. Requests for files that aren't in the tar archive would be prohibitively expensive.
There are definitely ways to do it without those problems, though. They just wouldn't be quite as simple as the approach done for supporting zip.
There are definitely ways to do it without those problems, though. They just wouldn't be quite as simple as the approach done for supporting zip.