Money is a measurement of value, like popularity is a measurement of skill. They're both poor measurements, but very easy to apply, they cater to everyone's understanding and there's undeniably a correlation. Therefor they get used a lot and people lose sight of how poor they are in many situations. Numbers also allow us to decouple from the ethics of the situation.

Take healthcare. You would not put a price on your own life: it is priceless to you. Nevertheless we put prices on other people's lives, because it is the easy way out, is accepted by almost everyone and allows us to avoid having to answer nasty questions. No one wants to honestly say someone unknown is worth nothing to them to keep alive. So you say you will only support health care up to $10K a year, because you know the chance a loved one will ever need more is extremely small. You talk abstract numbers to prevent from having to admit to yourself that you just don't give a damn. That wouldn't fit in with our ethics, would it?