Those people who have actually tried Windows 8 on a desktop seem to fall into three basic groups.
Those who tried it and didn't like it for whatever reason, and returned to Windows 7. Some may try the next version if it includes the option to boot directly to the Desktop and has a Start Button. Others didn't really want to leave Windows 7 in the first place.
Those who installed a third-party utility to turn it into an enhanced Windows 7. These people, like you, would be happy for the option to boot directly to the Desktop and have the Start Button - provided it didn't just go to the current Start Page. The question is, would they be willing to pay for it.
Those who (like me), with a little research, made the UI work for them. We really don't care if the option is there or not.
What we must realize is that we desktop users are becoming a minority (percentage wise). The growing majority is the mobile set. People whose job requires mobility (on-the-spot reporters/reviewers, salesmen, paramedics, and others) don't need a desktop, or even a notebook. Smaller hand-held devices are getting more powerful and have greater battery life, which makes them more suitable for work in the field. Their users really don't care about the Desktop and Start Button. So, realistically, how big of a market is there for returning these features? I mean in terms of percentage and money.
On the other hand, I can see MS complying with your request. After all they provide backward compatibility for hardware and software, so why not users?