xorg and it's problems is so funny
Most distributions still use a "Live CD" format, actually a "Live DVD" nowadays (with a few hacks to make it also work as a USB pen drive image), for their installers, and that limits the installation image size (which also includes enough packages for an offline install of a desktop environment) to a bit more than 4GB (they fit into a common 8GB USB pen drive). So it being the "age of Terabyte HDDs" does not matter, for packages expected to be installed on a normal desktop system.
Any USB drive is so super cheap these days, you can easily get something like 128 Gb for $15. Even if you live in an area where it’s not as easy (e.g. not very developed places), you’re likely to find, say, 32 Gb for less than $10. So I don’t know, maybe someone needs that 4 or 8 Gb limitation, but I believe it’s a non-issue in most cases.
Also, on top of that, we do have a very speedy Internet I’m so many places. Which means if you’re limited here, you can go with the net-installer. If you’re limited on both, more likely it’s a very niche case and you can have a spare large disk to download everything offline.
But neither does the "size on disk" because the ACTUAL size on disk might be reduced by gzip/bzip2/xz/zstd/whatever is invented later. Even if the program using the package doesn't support compression, it supports filesystems and filesystems often support some kind of transparent compression. It isn't a hard problem to solve.