How is a researcher different from a consultant?

Last week, I explored the difference between an advisor and a consultant. The question stimulated a strong response (thank you!), thus this encore. The difference between a researcher and a consultant might seem to be more clear cut. Most of us think of researchers as those boffins that inhabit our learning institutions, whereas consultants are typically suited and found in business environments. Does that make them completely different beasts? Consider this:

• A researcher defines problems and tries to solve them. So does a consultant.
• A researcher is a knowledge worker. A consultant is as well.
• Researchers tend to work alone. Many consultants do as well.

At this level, the roles appear to be very similar, so are the two terms simply two different names for a very similar activity? Possibly, but I don't think so. A key difference between the roles is emphasis. A consultant is most interested in practice, and good consultants use theory to contribute to their work. In contrast, a researcher is most interested in theory (be it testing theories or developing new ones), and good researchers use data from practice to inform their work (testing theories or developing new theory).

The roles are different, but they are closely coupled. Given this, why do so many consultants look down their noses at academic researchers (and vice versa)?