Because I use a Maestro card or cash. Visa / Mastercard simply does not fit into my mindset: they are credit cards, and as long as I am gainfully employed, why would I need credit? Credit is for the times when you cannot afford something.
Not having credit cards is a classic commitment device. Getting into a mindset of buying everything on credit then paying it off at the monthly payday is a bit of a slippery slope (no fallacy: there is an actual mechanism of slipping here: basic human desires), only one step away from buying everything on credit and then NOT paying it off due to overspending or other reasons. Only spending money one actually has is a generally good safe habit.
I would change my mind if there would be rewards like frequent flyer miles tied to credit cards but they are not common here.
About the reasons - Maestro is not entirely unknown in the Anglosphere given that most UK bank accounts are also linked to a Maestro card, and UK-based websites are fairly good at accepting it. Ignoring a market of a few hundred million of relatively well-to-do people is something that only perhaps be justified by time i.e. it is on the to-do list of the major US based online vendors, just not done yet.
why would I need credit? Credit is for the times when you cannot afford something.
You're misunderstanding the point of credit cards. They are not about borrowing from the bank (well, they could be but they should not be). They are all about convenience.
I use credit cards. I never ever had a balance on any of them -- I pay them off each month. It is convenient (and pretty much necessary for certain things like renting cars) and I do not borrow anything. I don't have slippery-slope problems with respect to buying "on credit". Oh, and at least in the US finding a credit card with decent rewards (typically, 1-2% of your purchases refunded to you) is not hard.
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