After a while of being on an app the local area appears to be quite stale, and it starts to become a requirement to scroll through a long list of familiar faces (who you've either already liked or don't want to like) just to find anybody new. A filter would allow you to only see users with an account below a certain age, which would practically guarantee these are people you've never seen before. This was a feature I found myself using a lot on Howlr.