Do you have exceptionally laid back people calling you? If I waited five seconds from picking up to speaking I’d always hear “… Hello? Anybody listening? Hello? …” from the caller.
(an aside: I always wonder how anybody can realistically afford not taking calls from unknown numbers. I very often leave my mobile number as a contact for businesses, etc and do not enter their number into my contacts. I also leave my number with the master of a building business for necessary repairs, and get called days later by a journeyman of theirs, from his mobile number. The vast majority of calls that I get from unknown numbers are legitimate, and in my interest to answer)