Or a relative get hurt on the other side of the country.
Or been seriously ill.
Or unemployed.
Or had a major appliance break.
Or a million other things that happen to people every single day.
In both cases, higher risk of default, less chance of profiting from interest, lower creditworthiness score!
So I got 3 credit cards and used them each during each month so that I would established on-time payments on all three and boom, I had perfect credit after a couple years and qualified for a mortgage. I didn't use any credit before I decided to buy a house in my 30s so I had a completely empty credit history prior to that, apart from a library that reported a lost book. So it just took a little while to get my average account age up and my number of on-time payments above some threshold.
Now if you don't use the card at all, it is less effective at establishing credit because you don't get the on-time payment history or balance. The credit bureaus just get reports of on-time or late payments, balances, and delinquencies/defaults, etc.
You will be given the best rating at a small non-zero percentage of your total available credit being used each month, but it doesn't have to be carried.
All you have to do is make sure you don't pay it off too early. Just wait until the due date, and pay off the statement balance, not the full balance. If you pay it off mid-month, before the end of the statement, or paid the full balance instead of what is due, you may get a zero balance reported which is a slight temporary hit to your score, but not that significant. I found that it was best to have a few cards with a total available credit at least 5 times my monthly spending. That way the reported balance ends up being <20% of my total available credit which is near the sweet spot. If I am going to do a refi on my house i might try to micromanage it to somewhere close to 5% for a few months ahead of time and get a few points added to my score, but once you get your score up around 800 it doesn't really matter if it is up or down 10pts or so. I found that as my average account age increased, the swings from slight differences in balance were smaller.
People who don’t use credit often get penalized from a scoring perspective because they don’t have a large credit line and have a higher utilization.
The bank wants you to make payments, period. More credit lines means you have more resilience.
The month I paid off that loan, my credit score dropped precipitously.
In 2006, my wife and I bought a home, and had to get two separate loans to make it work, because our credit scores weren't great at age 26, since I generally avoided credit.
As soon as we opened those two loans, our credit scores jumped to the highest they've ever been.
That and other patterns I've watched over two decades are why I believe credit scores are entirely about how well you pay the banks' game.
https://www.ftc.gov/faq/consumer-protection/get-my-free-cred...
If you are interested in how FICO scoring works there is a lot of information available on various forums. The best resource I have found is on https://creditboards.com/. The FICO algorithm is proprietary and they do not disclose it, but through experimentation people have managed to reverse engineer quite a bit of it.