When I ordered a Dell through the corporate account, we had a choice to order Windows OEM, or Windows Volume. They'd inform MS of the order, as per our agreement, but we could retire a piece of hardware at the same time, and we'd have our licensed volume OS delivered installed (with our corporate image), at something like a $10 cost. But then, this was a 10,000 person company, with a 4 year refresh, so a few thousand computers a year.
Having the corporate image pre-installed on the PCs was great, and only an option with volume licensing. So there is value somewhere, but not for the 100 seat company, they are almost always better buying with OEM installed.
The real reason MS pushes for no no-OS option is they know so many OEM licenses exist that someone retiring a computer could buy one with no OS, then move the OEM onto it, and at least appear compliant at a glance. Move the sticker or swap the case, not a huge deal for a 100 seat place with 3-person IT, generally 2 help desk to do the grunt work, and one "manager" to hire the consultants to do the real work. The help desk guys sit bored, and can spend all day swapping hardware to avoid a license cost.