What's wrong with building a $50 million dollar business?
It's brain melting difficult to build a $50 million dollar business. If you can get to $50 million, you might as well up the ante, and just say you're going to create a billion dollar business. Because the curve on difficulty is off the charts either way.
It may be true that the number of $1 billion exits per year is only, say, 10 times fewer than the number of $50 million exits. It's an empirical question. The numbers matter.
Let's just raise the $1 billion number until it's a better bet to go for $50 million. At some point the argument that "both are just absurdly big numbers" breaks down.
Perhaps the reason people think that the numbers don't matter is because they believe that the skills required to build a $50 million company is no different than those required to build a $1 billion (or $100 billion) company. That I buy.