I've been asked to provide financial information due to accessing sensitive sites while working before. It was as part of an enhanced security clearance form. I had to give details for myself, DP, my parents and if my parents were separated, their partners too. This was some years ago, shortly post 911. Not sure if this sort of thing still goes on.
The police, Prison Service, Miliatary and probably other similar employers expect their employees to keep their finances in order (payments up to date, no unmanageable/large debt) as financial difficulties is seen as being vulnerable to bribery. Not saying it's fair or right, but they are the rules.
I'm another one who uses credit cards to my advantage. I pay them off in full every month and earn cashback. I find it easier to spend this way and treat the monthly credit card bill as another bill. Otherwise you have to separate spending money from direct debit money in your current account anyway, otherwise you need to keep track of what is needed for direct debits and what you can spend before payday.
I have money borrowed at 0% fee free that is saved in interest paying accounts paying up to 5%.
I recently got all my money back from my credit card, including the cost of more expensive replacement flights when Monarch went bust a couple of days before we were due to travel. Incidentally, I also had scheduled airline failure cover on my travel insurance, but that turned out to not be worth the paper it was written on so wouldn't pay out.
If you use credit cards to your advantage, they can be useful and profitable. It's only if you don't do they get you into trouble and are not worth having.