Including the scriptlets from https://fedoraproject.org/wiki/Packaging:ScriptletSnippets#Icon_Cache in a package's .spec file if the package includes an icon seems redundant (almost every GUI package contains those scriptlets), is an additional burden for package maintenance and looks a bit hostile for new packagers.

Almost all other scriptlets have been converted to triggers in the appropriate packages. So, aside from ldconfig (where there is ongoing discussion about a possible implementation of triggers), the icon cache generation is almost the last thing left in fedora 25+ which requires scriptlets being present in .spec files.