Cofounders are not great anyways of either type. If you are a business person, learn the tech stuff you need. It's easier today than ever. If you are a tech founder, it's even easier to pick up business stuff than tech stuff.

Investors always encourage it because it reduces their risk... One of you can be fired and they still have the backup. But when it is all on you there is no passing the buck.

Source: solo bootstrapped founder of a company earning $1,200,000 a month for the last sixteen years.