I find - and this is a grand stereotype/characterization - that often men tend to be more pragmatic about spending. Meaning, they look at their bank account, know what money they have to spend, consider what bills are coming up, and then decide about making a purchase.

On the other hand, women tend to look at it through the lens of what is needed. If something is a "need", then you buy it - regardless of what is in the bank account. It's a need. You have to make the purchase.

At least when it comes to couples fighting about finances, this is what I see. There are also times when the wife is more pragmatic and the husband is more quick to purchase "needs". But more often than not, it's the other way around.