There are several threads in ATMB about what’s useful about the friends feature and what requests do or don’t see when approved / denied. A quick search will give you authoritative answers from TPTB.
The short answer, IIRC, is “not much”, and “nothing either way”. vBulletin has many fancier “social” features that aren’t switched on here. “Friends” is the visible tip of that submerged iceberg.