My hot take is that men with extreme wealth and power are desperate to keep it as part of their identity, where the women I mentioned do not have the same character and personality flaws, and therefore use it as a tool to do good because they are not optimizing for status, power, and wealth: they are optimizing to do good. Doesn't always hold, there are exceptions.
"Power tends to corrupt and absolute power corrupts absolutely. Great men are almost always bad men, even when they exercise influence and not authority; still more when you superadd the tendency of the certainty of corruption by authority." -- Lord Action
I think more likely is that bill and Jeff built their wealth through their businesses, which they are still directly involved in. Giving away their wealth would be equivalent to giving away the business they built from the ground up
I think there's also a question of efficacy. Bill and Jeff are really good at turning $1 into $10. Melinda and Mackenzie? Not so much. If bill or Jeff wanted to maximize the amount they can give, the best strategy would be for them to continually earn until they die, and then donate it.
There's a difference in men and women... until there's not. Very convenient.
One giant exception was Chuck Feeney, who made $8 billion on duty free shops and gave almost all of it away, much of it anonymously. By the end of his life he and his wife had a couple million and lived in a rented apartment.