boot13Lifehacker has an interesting post that points to information from Microsoft on downgrading Windows 8 to Windows 7.
The downgrade option is not available for all new PCs and license types. The Microsoft page linked above goes over the details.
There are a lot of legitimate reasons one might want to downgrade.
It’s no longer possible to purchase a PC with Windows 7, so anyone buying a new PC will get Windows 8 by default. Being forced to switch operating systems by a big corporation is annoying for many people. You know, people who prefer to have a choice.
If you’re not interested in learning the new O/S, or setting the computer up for someone who is comfortable in Windows 7 (say your grandmother) and doesn’t want to change, this is a useful option.
I’ve personally downgraded a set of Windows computers like this, when software required for a business just didn’t run with the delivered O/S. Sure, it’s the developers’ fault, but waiting for a fix wasn’t an option.
You may use hardware and/or drivers that don’t work on the new O/S, in which case, again, you don’t have much choice until you buy new hardware or (if you’re very lucky), the hardware maker produces new drivers.
Corporate IT providers use the downgrade option more than anyone. There’s a constant need to replace aging PC hardware, but upgrading operating systems involves an enormous amount of re-training that most companies would prefer to do on their own schedule, instead of Microsoft’s.
And so on.
Suprisingly, a lot of the comments on the Lifehacker story are negative. “just learn the new O/S” is a common refrain. Unpaid (or possibly paid) marketing drones, all of them.