Should it? Isn't that irrelevant to how fast the "best of the best" can get to 50 Mil?

True, but if you want to calculate your own EV over x years, you need that kind of data.

This was starting with the premise of "success" -- let's assume it's a world class idea and hits $50m in revenue, goes public, and becomes one of the top 100 software companies in the world (in terms of capitalization). How long does that kind of amazing success take?

If you're wildest predictions about growth of your startup are off from what the historically most successful companies public today are doing, that's worth looking at.