Ateendants or maids in black desert are very useful feature that allows you to move stuff from storages to your inventory remotely. If you mean attendant as just character we can customize to appear as one of your maids then its purely cosmetic.

The customizable attendants, not the maids and butlers whose appearance you can't customize, are basically only for taking screenshots or videos. Kinda fun if you're into that sort of thing. Otherwise no. It'd be neat if we could fight with them and stuff though. I suppose that would discourage people from partying up with other players though.