Not force, no. But it's like doing conversation practice with EFL students (something I have done a lot). You learn to phrase questions in such a way that it's very hard to give one-word answers, otherwise one-word answers is all you get. Not as a deliberate refusal to co-operate*, but as an easy get-out/line of least resistance.

I would say that some incentive to expand on the bare minimum within the framework of the game would be a good thing. Loquacious people don't need much help to break the ice in any case, it's the shy ones who are naturally reticent that need the motivation.

*Or at least, not necessarily.