to increase your "credit score" (needed if you want to get a mortgage or rent a place), you need to own at least 5 credit cards for many years and show that you keep borrowing and repaying every month (otherwise your credit score is lowered)

I can attest to that. My parents and I immigrated to Canada (yes, not the USA, but close enough with a similar enough system) when I was 9yrs old. I remember when they saved up enough money and tried to buy an apartment unit when I was 13. The banks didn’t want to give my parents a mortgage even though they had 40% down payment on hand and sufficient income to prove they could repay the monthly payments. The reason was that their credit score was low; and the reason for a low credit score was that they always used cash and never used a credit card. My dad ended up having to get signed guarantees from a few builders (he did contract construction work and was self employed) to secure that mortgage. My parents were never in debt, always paid every bill ahead of due date (with old school mailed in cheques), and always had a good amount of savings in cash and in the bank. But their credit score was bad because they never used a credit card and never went into debt. Strange world…

many companies offer their own "rewards" credit cards and use it as discount card (like every airline, bigger malls and shops, etc.) and they try to upsell you when you e.g. buy a new pair of jeans

This one pushes consumption a lot. They give you “points” back for spending with / using the card. But these points can only be traded for consumption goods, most popular are airline tickets and hotel bookings. This means they encourage you to go on more vacations by using these points. I mean what better way to spend and consume your capital than a vacation? My sister-in-law is big into these “travel points”, and always ask my wife why we don’t get one of these travel point rewards cards. My wife is interested too, but I tell her that I prefer cash back on the credit card; that way, we are not incentivized to go on vacations and forced to consume.

One thing I would like to add is that the credit card companies make it very easy for a young person to get a credit card, as soon as they become a legal adult. I remember there was a credit card booth occasionally setup in my university, in the hallway, helping students sign up for a card when I was in my first year. That was how I got my first card when I was 19 (legal age in Canada). They then encourage spending and mould your mind to live the fiat consumption lifestyle; buying all these cheaply made plastics and going on vacations, basically just consuming, all with credit. All at a young age when you didn’t know better and easily manipulated.