From what I understand it's basically for two reasons.
First is that even if the SSID is "hidden" it's still easy enough for someone who knows what they're doing to discover its existence. With wireless signals flying through the air, it's impossible to fully hide an access point.
Second is that it draws attention to you since you're different. If someone were to attempt to brute force the password, they'd possibly think that a hidden wifi makes the owner think using an easier password is okay. Or maybe they're hiding something interesting.
Overall I don't think it really matters that much if your AP uses up to date protocols and you set a unique and hard to guess/crack password. Don't let your dad pick the password.