The "majority" of people probably aren't clicking on untrusted links either, but we still advise people to keep their browsers up to date. Many people also need to open .docx files from strangers because it's part of their profession/business. Small business owners need to read RFPs and pay invoices, and jobseekers might need to open a questionnaire from a potential employer, all of which could be in .docx. The sender doesn't even have to be malicious. It's possible for one person, who's used to opening untrusted documents on a regular basis (eg. recruiter), to get infected, and for the malware to infect other documents that person sends to others (eg. finance).