I think it's in large part due to documentation and fonts. For example in my Fedora, I only have part of texlive installed. My /usr/share/texlive/texmf-dist is

I think it's in large part due to documentation and fonts. For example in my Fedora, I only have part of texlive installed. My /usr/share/texlive/texmf-dist is 1.3G, of which 428M are inside the doc subdirectory and 639M are in the fonts subdirectory. Then there are many packages that contain pictures or logos. As a single random example, texmf-dist/tex/latex/fithesis is 2.4M, of which 2.1M are in fithesis/logo.