If you're going to downvote me, please explain why. I'm honestly perplexed.
On the flip side, they may have a sense of responsibility to contribute more, but no gauge of when the contribution is enough. If the government makes that decision, then they resolve themselves of making the judgement.
Because let's be honest, it's not like their living standards would be significantly damaged by paying a few more millions to the treasury.
In any case, you have to ask yourself why they're advocating for this stuff in the first place. These billionaires have international wealth. Raising the taxes fom them in the US is just going to drive capital overseas. It would make it harder for US-only business to compete with the international conglomerates if US taxes were raised.
If you want to see improvements domestically, it has little to do with income taxes. You need to raise tariffs and outlaw subsidies to businesses ("I'll give you 50B to build your new stadium in nowhere's-ville"). They'll be forced to invest domestically, pay domestic wages, pay for the infrastructure they need to support their businesses, etc.