Having money means having buying power. Spending all your money on stuff you don't need or want, however, reduces the power your money has to actually improve your life. Being content, counter-intuitively, gives your money more power.
As personal finance site Finance Yo Self explains, your money is only as valuable as you treat it. For example, if you spend your money on a reliable car that lasts for over a decade, that's more worthwhile than blowing hundreds of dollars every month for four years on expensive restaurants you didn't enjoy much to begin with. When you blow your money on even more frivolous things that you don't enjoy, you devalue the money you have:
The most important thing I've realised is that some dollars are more powerful now than others. Any dollars I spend above a certain point are almost worthless. Sure, they give me buying power today, but what is buying power worth when you already have what you need?
So, being content makes it possible to reduce how much money you spend on things that don't really improve your life. The more you reject spending money to bring a fleeting high, the more money you can save on the worthwhile expenses. You literally make your money worth more to you by spending it on the things that bring you happiness.