Because the pool for a CEO hire is much smaller, than "people with MBAs" as has been floated in thread elsewhere.
If you want to hire a CEO, you either usually are looking either at A) A CEO of another company with experiences relevant the current situation, at a size similar to the current company's size. Or B) A senior exec (CFO, COO, etc ...) at the same company, or more rarely an involved board member.
Why would it?