It's not really about being the only user, or worrying someone will accidentally delete your character, it's about keeping your information safe. Unlike destiny, FF14 is a p2p game, it has your payment information on file, which needs more protection. On top of that, unlike destiny again, FF14 has an RMT community always looking to steal people's accounts for their items and gil that they can sell for actual cash.

Personally, I don't mind taking an extra minute tops to make extra sure my CC info and character have strong protection.