Utility vs enjoyment, Which do you choose?

So far, I’ve only studied (and am still studying) languages that are considered "useful" by society. But when I tell my friends that in the not so distant future I want to learn Friulian or Indonesian, they say those are "useless" languages and that I should be learning German or Chinese instead.

When you’re deciding on your next step in language learning, what’s the main factor behind your choice? The utility of the language or the fun and enjoyment of learning it?