I use credit for the purchase protection (I believe many debit cards have this as well but it’s easier when you haven’t yet paid the charge, and seems better enshrined in law for credit), for the rewards (which including signup bonuses can be huge), for the float period, and for security — if somebody fraudulently uses a credit card versus a debit card, there’s no actual money missing while the situation gets resolved.

In germany a similar scheme exists (Schufa) but it's less important.

Yeah, it's all a huge con. The best fiscal habits involves not spending money you don't have, so you should never need a CC to begin with. But if you take that route, you end up being unable to finance a car or apartment because companies can't snoop into how you spend money. So you're forced to either play the game or be so rich you can buy everything you need in cash (which, ironically qualifies you for the best kinds of CC's anyway).

Now, if you DO manage to that threshold... you still want to delay finances. Because installments now become ways to give your money more time to make money and offset whatever you are paying for. The models and incentives are completely at odds.