My two cents:
I think it can help to think in a more “developing” way, like you were already told; I don’t think the specific algorithms are necessary in every front-end-exclusive-job but they even help by just forcing the user to go and read (or ask) about stuff that he doesn’t know about, which is a very important skill (knowing what to search, that is).
Also, they give a sense of satisfaction when solved which, again, I think it’s important to a people state of mind. It keeps them going.
With that said, there is a thread from a user who got a job focusing on projects instead of algorithms; it all depends on what you want to do and what you are good at. There are people who suck at algorithms (me included) but excel in design and there are people who, instead, are a natural at algorithms; there are jobs for both those kind of people.
From my point of view, FCC algorithms challenges are just that. Challenges. You are not forced to do them and there is no indication that being good at them will grant you a job but they can help to, well, challenge yourself, think, and maybe learn something you didn’t already know.