If you play on PC, definitely get a token. Stolen accounts always have been and always will be a hot item, and unsavory types are always finding new ways to slip through the cracks. As an example, I remember an incident during the days of FFXI where a browser pop-up add introduced a keylogger or something into players' PCs, and a number of FFXI players accounts were stolen as a result. The pop-up was common on sites FFXI players went to for game info - so, basically, players were losing their accounts simply by browsing the same websites they usually do.

While that little trick would likely be difficult to repeat nowadays, the search for security vulnerabilities continues, and no system can be said to be 100% safe. You don't want to be part of the 0.1% of players affected when someone manages to find a way in. Multi-factor authentication is a huge step-up in security.

If you don't play on PC, you're less of a target, but presumably you still have to log into the Mogstation from time to time, for instance to chance credit card info when your card is about to expire.

Having to enter a six-digit code every time you log in might seem like a pain, but it's really not that bad. The extra security is well worth it, and the free teleport is lovely, as well.