The people who would buy computers with Linux probably wouldn't pay for tech support. Enterprises might, but not individuals. Plus I suspect that Microsoft is pretty keen to defend Windows on the consumer front - I've heard stories of deep OEM discounts on the condition that they don't offer alternative OSes.
I mean in the same way you buy a Dell notebook and get two years of phone support, you would get the same with a Dell Ubuntu notebook but Canonical would provide it and Dell would pay them for it.
I mean that the people who would buy a Dell Ubuntu notebook mostly wouldn't use phone support. If Dell thinks the same, they wouldn't pay Canonical very much to provide that support. They do now sell the XPS 'Developer edition' with Ubuntu; I have no idea whether they pay Canonical for support, or how much that makes.
