Their wealth made it way too easy to create spoiled, entitled brats, and she really wanted to avoid that.
I personally never had that particular problem and had to say no to my kids aplenty out of sheer necessity. But I found her words and attitude very wise.
Understanding that just because we have enough money in our pocket or bank account to pay for something does not mean that we should do so is a very valuable life lesson to pass on to our kids.
It’s also something adults would be well advised to remember.