.docx and .xlsx can only be read on a small subset of devices and only after purchasing a license. It is frankly a bit rude to expect everyone to have such licenses in 2022 given the proliferation of superior, and free, alternatives. If the document is static, read-only content, convert it to a PDF. If it’s something you want me to edit or comment on, or which will be changing with time, send me the document via Microsoft 365 or the equivalent Google offerings. Or a Git repo. Sorry to be grumpy but everyone should know this by now. If you’re still emailing these around, please stop.
No license required if you use LibreOffice, etc. Still incredibly annoying, though, and I also hate the assumption that this is a reasonable thing to do.