As a non-american I have to ask: why sign up for new credit cards all the time?

Because credit card companies offer incentives to sign up for their cards. A lot of people here regularly carry a lot of debt on their cards, and the credit card companies know if they give those users more cards to juggle around their debt on, they can leach more money from them.

For financially responsible people, that means you can sometimes get a few freebees if you're willing to deal with the hassle.

I don't know what it's like in most other places, but debt is a weird part of culture here.

I'm British, and while some people have credit cards, most people I know don't. I have a bank debit card and I use the single card to pay for pretty much everything I don't pay for directly with cash. I have zero debt, because I always pay up front for everything.

I do get lots of junk mail for credit cards, have done for decades, so I could get one tomorrow if I desired. But I don't see any real value in doing so; why get into debt if you can avoid it.

I use a (n.b. singular, not multiple) credit card from AMEX for the benefits. (Particularly excellent travel insurance and car rental benefits.) I make sure to never spend more than I can pay off at the end of the month, so that I don't actually ever get into debt. My own money is resting nicely in a bank account until the credit card bill arrives.

I never spend my own money directly unless I have to (e.g. the merchant doesn't accept AMEX or only takes cash etc.) because should I end up with fraudulent transactions or lose my card or whatever it may be, I have actual cash to back it up.

If you're fiscally responsible and make sure to always pay off the bill at the end of the month (with all that money you didn't spend) then credit cards are pretty much nothing but benefit. There may be a yearly fee associated (my card has one) with it but I've found it to be worth it for the benefits alone, but I also rack up so many points that I can use those to pay for the fee.