I've had this same thought, and have a pet theory about it. I think the answer is something like momentum is so unbelievably useful in business that having it is enough to be immensely wealthy and successful.

As someone who recently created yet another startup, I am reminded daily that literally everything I do has to be done for the first time. It's like molasses covering every part of the machine. When a client needs a proposal you have to write one from scratch, when someone wants payment terms or to negotiate a contract adjustment you have to figure out contract language. You don't have expense reimbursement forms, you don't have job descriptions, you don't have anything to use as a starting point or template for anything you do.

Big companies have all that. They have clients that are planning on using them again this year. They have meetings they took two years ago that are about to be a sale. They have a guy on the third floor that has seen this problem they're about to have once and knows how to avoid it. People instinctively trust them, so they don't have to explain themselves as much. People instinctively fear them, so their contracts get upheld. People that used to work for them now work at potential customers and call them up.

And on and on and on. Having a slightly busted software development process is, in fact, peanuts compared to all this.

Or, perhaps another way to say it is that there's a lot of different kinds of "software" besides the digital ones-and-zeroes kind we think about here. A group of humans all organized around a business purpose with tons of experience and momentum is a high functioning machine as well.