[Kevindish]

I think that is because that under 5 chars, there is not that many usernames.

It would also be odd with a username on only 1 char?

[iamjonlee]

I think there would be a lot of personalized usernames, which is what I'm going for. Imagine having having a personalized link like domain.com/jon or domain.com/tim. There's definitely a lot of demand for such personalized usernames.