What’s up with people making random posts asking for all sorts of info

I’ve seen many different posts and it’s usually people asking to post either your last name or the initials of your name. Sometimes it’ll be a picture or name of your pet or the day you were born. They do it as a fun “little trend” but is it really harmless?? I never participate in these because why would I give a stranger any of my personal info? I find these trends weird.