Do you work at mcdonalds OP? Jokes aside most people are fucking awful with money and dont have spare cash to invest. Why do you think amex gives out a fuckload of airline points if you sign up for a credit card? If you have a brain you can just do the minimum and cancel it and pretty much get a bunch of free flights. Amex can do this because for every smart person there are 1000 idiots who only make the minimum payments.
Take cars, instead of buying an older car with cash they finance a new one or take out an expensive lease with all the bullshit extras. Then comes the mortage or rent that is above what their budget should be, all eating into their income and barely leaving anything leftover for a rainy day. Add in a few more montly expenses and it keeps chipping away. Normies kneecap themselves financially in ways you wouldnt believe, but because they are all doing it you percieve it as normal and okay.
Boomer advice aside - look at Dave Ramsay's youtube channel and the kind of people who call in. Huge credit card bills, car payments, timeshares, caravans, blown out student loans, all avoidable debt.
