Not being on social media (except this one obviously, and generic messaging apps). Missed out on a lot of potential friendships because of not having insta, or snapchat, but it's something I just can't bring myself to do.

EDIT: I wish it was more normalised to share phone numbers instead. It doesn't have to be reserved for dates ffs. However people of younger generations seem to think it's weird or unnatural to ask for someone's phone number etc. Either that or people just used Signal instead - no number required.