AutoCad is considered a “must-have” application for some end-users of PCs and some give that as an example why GNU/Linux does not take larger share. In truth AutoCad is used on a rather small number of PCs in total. Not everyone is a designer/draughtsperson.
For many years AutoCad was not available on MacOS either, in spite of MacOS having a resurgence in business. That is changing as AutoDesk announced that AutoCad is coming back to MacOSS. As the same hardware runs GNU/Linux and MacOS is a UNIX-like OS it is quite possible that a release for GNU/Linux will appear sooner rather than later. That should shut up some of the trolls who insist availability of one app is the cause for GNU/Linux to have a small share on store shelves.
Globally GNU/Linux has a larger share of PCs than MacOS because Macs rarely appear in large parts of the globe. The USA/Europe regions account for only about half the world’s PCs and AutoCad, while useful, is not essential to everyone. At $4000 it is not affordable either.