Don't Add me: If you try to scam.
Don't Add me: If you beg for free items ( I choose when and to who I will give free items )
Don't Add me: If your profile is private. ( Except if you have reasons to do so )
Don't Add me: If your inventory is empty. ( Or you need something important from me )
Don't Add me: If your account has any of these ( Steamrep Ban, Trade Ban or VAC Ban )