There are many things that don’t do that, and even reduce the amount that rich get richer.
Consider a hypothetical blockchain where every account is subject to a tax of 10% per year, and the proceeds are burned. One might say that everyone is getting poorer, and the rich are getting poorer at a faster rate.
But of course there's no real difference. If every account receives a 10% reward or a 10% tax, we all end up with the same share of the token supply at the end of the day.
So it’s already really exclusive as only a very few people have $50k available.
There are also some sharded PoS designs where staking can be done in a really lightweight manner -- the process can be mostly idle, and only sync when it's the user's turn to do something -- even on a mobile device.