The reason these consumer credit monitoring services came into existence is interesting and, I assume, public knowledge, but I only learned about it when I worked for them.
Once upon a time governments in places with credit reference agencies (so particularly the UK and US for this story) noticed that this is a lot of power with not very much responsibility and they ought to fix that. So what they said was, you must let people see this data you know about them, for a small statutory fee. No option, that's what you have to do now if you want to stay in business.
This actually terrified the CRAs, because they imagined everybody is going to send off their fee, and it costs more for this enormous unwieldy corporation to respond than they're allowed to charge, so if everybody does this the company goes bankrupt.
But internally at Experian somebody says - Aha! The law doesn't require us to explain what the credit data means. So if you pay your fee you will get stuff that's incomprehsible to lay people not because we're deliberately obfuscating it, but because to us maybe "day 60 late ratio" has an obvious and very specific meaning but to a consumer it's noise. Obviously an expert could write a book about how to decode the statutory report, but we can instead offer a product that costs more than this fee but includes friendly explanations and translation. If we set the pricing right on this product, we make a profit while also warding off the statutory reports we dread.
And that project actually worked. As of ten years ago lots of people worried about their credit would cheerfully pay a CRA money to find out what the problem was. The division doing that grew enormously within Experian and other CRAs copied this idea.
In fact popular culture made things that didn't exist in one country (e.g. the numeric FICO score from the US) part of what consumers expected to learn in other countries, and so Experian UK actually has (or had when I worked for them) people who make up the formula for an arbitrary score number, even though creditors in the UK don't use this - so it's as meaningless as your Hacker News "karma" score.
Then somebody had another bright idea, what if we give this product which apparently people value, away for free, and then for a fee attach it to credit offers like new credit cards? We funnel card companies the exact customer profile they were looking for, they save acquisition costs, the customer gets the new credit they wanted, everybody is happy and we're richer. So that's what happens today.