Just because flexibility is allowed, it doesn't mean it's highly encouraged to play more than one. If there's any reference to what you're talking about in-game, I'd like to see it.

The options are there, but some people will never touch a crafter or gatherer or Tank/Heal/DPS. I think the expectation is that you'll find something you really like to play and prioritize that. That's the more standard approach. You're welcome to do the other stuff without the hassle of a job being tied to a character, as it is elsewhere.