How is that worse when the key is bound to the hardware and non-transferable anyway?

why would it be non-transferable?

OEM licenses are legally (and practically) tied to the machine. There’s no way to transfer it.

Sorry, I thought it was a reply to https://news.ycombinator.com/item?id=44581124

In case of OEM, the license is never directly owned by the owner of the machine; the license is tied to the hardware, and you're selling it on with its license key attached. If you activate Windows using a bought license, that license does not get copied into the hardware.