Why? Because I'd never gotten a credit card before. Had I simply moved existing purchases onto it, and taken the same (zero) revolving debt, I would have appeared as much less risky. [1]
What's worse is that when I went to the "what's my FICO"/credit report sites, they would consistently say that my credit score should be 740, even though this never translated into any observable consequences in terms of ease of getting loans.
And what made that even worse was that there were actual critics of the subprime practices then that refused to believe this was happening, that anyone classified as subprime must have deserved it in some way, even after I offered to forward this information over!
[1] Yes, I know, I should have known to pointlessly get a credit card and switch which buckets expenses go in, which is somehow informative about my credit risk.
The trouble is that the situation you describe is idealised and probably unachievable. In the real world, it seems more likely that a different, more complicated set of strict automated rules will be created, and it will simply create different loopholes through which some innocent people fall and get treated unfairly as a result. There will just be a lot more loopholes with fewer people falling through each one, making the system as a whole less accountable.
I learned a useful lesson just after I graduated from university. I had a decent job offer, I wanted to consolidate my modest amount of student debt into a sensible place as the student banking perks were expiring, and I wanted a small loan to buy a car to commute to that new job (which was far cheaper than either moving or taking public transport). I went to the bank I'd been with for years as a student, with all the paperwork including the signed contract for the new job, and explained what I was looking for. The guy I was speaking to looked a little sheepish, said that he thought what I was asking to do seemed perfectly reasonable... and then off the record suggested I didn't formally apply for it, because he already knew the computer would say no. My new job didn't start until the following week, and apparently that would mean the computer would have considered me to have no income at that time and so all the application would have done was get an automatic refusal and a mark as such on my credit record.
I think the moral of the story is that more data is only as useful as the analysis you make of it, and trying to codify and automate matters as complex as a typical adult's financial affairs is unlikely to lead to a reliably good analysis. In fact, I think it's even the law in my country these days that any such automated decision has to be reviewed by a real human on request, which might or might not be worth much in practice but does give some idea of the scale of the problem.