To expand on what Yogthos and RedClouds already said, the U.S. "consumer credit" system is also, effectively, mandatory participation from birth and you don't ever get a choice in it later on. There are multiple private agencies who track and maintain records of U.S. citizens' credit history. A typical person here will do business or apply for jobs at many companies over their lifetime which will check these credit histories and/or submit that person's payment records to the agencies as part of the business (like mobile phone service contracts, credit cards and car loans, corporate landleeches and your monthly rent history, etc. etc.).

I think the way it works is, the first time you do business with a place that reports to credit agencies when you turn 18 or whatever, your identifying info is sent over and your personal credit history begins. It's like having an account created on your behalf at a shady, unaccountable business from which your data can't and won't ever be purged (bonus: your personal info has a good chance of getting stolen from said agencies and sold on TOR forums every few years or so).

If a credit check is part of the employment process at some job, their HR department is using it to determine how responsible and trustworthy an applicant is expected to be. Banks and finance jobs always do this as well as other non-finance but high level jobs. Someone with large amounts of current debt or history of missing payments on rent won't get hired at such jobs because they're considered bad with money and desperate or irresponsible, a liability for theft and embezzlement as the employer would see it. Same principle when applying for places to live, low credit score or red marks in payment history = no housing for you.

The system has a bunch of stupid guidelines for maintaining a high 'credit score' that are taught as sage life advice in a lot of high school, home economics classes here, probably because this shit is so deeply ingrained in every aspect of life that it's inescapable. That 'credit score' is a three-digit number ranging from about 500 to 850, it's often listed with some minimum required score on housing applications and similar, it is used as a quick judgment on your history of borrowing from and repaying capitalist entities, higher number being better. It's calculated by a an algorithm and nobody knows what the algorithm is because it's an industry secret. The score is updated regularly and we can get a free copy once per year of everything on our personal credit reports from each of the three "main" credit agencies, if we request one.

Unless you're so wealthy you can buy everything with cash, having no credit history at all or a bad credit history can significantly impact your life comfort and ability to find housing, so we are forced to play this fucked up game.