I will consider setting emergency funds as necessary and essential for everybody irrespective of how rich you are, there should be what can be considered as your emergency funds based on your finances status, we can't say that because we are so rich that we can should not have separate emergency funds.
There are rich men that don't even like keeping or saving a lot of money, any money they get, they tend to invest them in one project or the other and some big men run out of money sometimes, not because they are broke but because they have invested their money somewhere while expecting the returns so within that period when they don't have money they can borrow from the bank so what am trying to emphasize is that even as a big man, they should keep emergency funds because if they don't and run out of cash due to the fact they have invested all their money, it will become a problem because if they go to borrow money from the bank to solve an urgent need and the bank do not grant them, they can fall back to their hodling and sell part of it to settle that urgent need which is not a healthy practice for an investor who is trying to build their portfolio, regardless that they are rich.