Every single person in society weighs up their options and decides what works for them. They'll be altruistic to a point, but always balancing the cost to them versus the reward of what difference their altruism makes.
You are pissing in the wind if you think that will ever change. It's the result of hundreds of millions of years of evolution, and it's appropriate adaptive behaviour.
It's why you haven't sold all your possessions and handed over the lot to charity in return for sleeping on their shop floor.
High earners are already giving away huge amounts above their fair share to help everyone else in society. Whilst more than 1 in 5 of the working age population aren't actually working. There comes a point when you say 'no more' and cut your losses.
Incidentally, for obvious adaptive reasons the point at which you say 'no more' does depend on whether you think society will return the favour if you need it. Calling high earners selfish, vilifying them in populist rhetoric, comments that their children should be taken down a peg or two: that all speeds up the point when higher earners cut their losses and opt out.
If you think you would never feel that way, then I'm willing to bet that you're below or not that far above the point where your tax contribution covers your per-person cost of running the country, which is about £40k income. So in that case, you're getting great value for your taxes.
I felt pretty proud to be paying more than my share too at one point. Not any more.