If you live debt-free then you shouldn't need to worry about what your FICO score is. Or am I missing something?
Maybe.
Well, sort of. FICO score is used an all sorts of things to determine what rate you'll pay. Credit rating plays into things like security deposits with utilities, insurance rates and, apparently, a protective employer can use them to decide whether or not to hire you.
These as well as more specifically insurers like to use it for rate-setting where allowed, too. They claim it shows a level of responsibility but they don't really word it that way for fear of being called on the rug for discrimination against broke people.
Certain types of background checks also will use them to see if you're more easily bribed than someone else, or as one of multiple indicators of impulsive behavior. Usually government classified type jobs but also some in financial and other areas where a person with a need for cash to get out of some sort of personal trouble could embezzle money easily. Or manipulate market prices of equities or other things.
Employers don't like seeing a bad score in those fiscal jobs or jobs where you're holding secrets like information that must not be released in a public company to anyone giving them an advantage to trade your stock, for example... and there's a reason those jobs often pay better than average. In theory, it's harder to get into debt trouble if you're paid higher than average.
In reality, this doesn't work, so your credit score is one of the "canary in a coal mine" signs they watch for changes in. In some of those jobs, so is your driving record. A sudden bout of nutty driving might be the first indicator they have that say, your marriage is falling apart and now you can be "bribed" with sex. Yeah, it gets that weird. I know more than one person who has to report any traffic tickets immediately to their Security Office and submit to a polygraph test that covers various questions already know in a baseline series of polygraphs, immediately, if the employer so desires.
Or so all the theories go. In practice they have a lot of indicators they watch when you work at those sorts of jobs. And they still miss bribery and affairs and such. Hopefully not as often as when not looking at all, is the operational hope.
Credit score is definitely one of those metrics some places use for "interesting" security stuff like that.
There are also multitudes of types of "credit scores" available from the three big agencies and there are also multiple types of FICO score, which are generally unavailable to the public.