What does the non-technical founder do that the technical founder can't? I have see alot of cases where the biz guy says he has the connect or he will sell the

What does the non-technical founder do that the technical founder can't? I have see alot of cases where the biz guy says he has the connect or he will sell the product but when its built, he expects the techie to come along with him and sell it. Or he simply says the connect fell thru. Alot of times I sit and think what would I have a business guy do? Write a business case? Write a marketing plan? Raise capital? Then I say to myself all these can be done by me and more than likely the the biz guy has just as much experience as me in accomplishing these goals. But the point is i'm confused about a biz guy's value.