It makes sense, if manufacturer provides support for Linux on the same laptop SKU. But that's very rarely the case. So selling laptop without OS seems like selling half-working product. When you're buying a car, it comes with a lot of software. ECU software, multimedia software (sometimes it's Windows CE) and so on.

I saw laptops selling with FreeDOS but realistically speaking I think that majority of these laptops end up with pirated Windows, so all it provides is increasing level of piracy.

Ideally laptop should provide a choice between Linux and Windows on the first boot. And easy way to buy Windows license if user chooses it.