MBAs are certainly not just for consultants and financiers - anyone interested in management could potentially benefit from one. It certainly is not necessary to start a business, but can be useful in any number of other fields and areas of specialty (operations, marketing, strategy, HR, and so forth). My B-school class is now employed in positions ranging from non-profit to I-banking, operations to business development.
The MBA is neither a ticket to wealth nor a degree as specifically useful as you suggest. It is simply another tool to use in a wide variety of areas. It is hardly essential in any job, but in a few it certainly does make things easier. All depends on what you want to use it for.
As for the suggestion that it's not useful because some VERY rich people don't have one, that's a bit of a stretch. While many entrepreneurs do not have MBAs (again, not required), many others do, as do many of the management upper echelons who do quite well for themselves. Money isn't the best measure of the degree's value.
Just my tuppence.
P
