While this is true to some degree, IBM/Oracle/SAP solutions are complex because the requirements are ridiculously complex. Could the requirements be streamlined? Probably, but that would require a wholesale restructuring of the way the company does business. Which, again, will probably happen, but usually not before the company ventures down the path of an ERP implementation and realizes how needlessly complex their business is. But there is a market demand for these types of products; they don't solely exist to fund the increasing size of Larry Ellison's yacht (though maybe in Larry's mind they do).
The main school of thought in business these days is still organizational and process focused. Only the newer guys think of business in terms of products, SOAs, SDGs and APIs, and it'll take decades yet for that kind of thinking to fully infect corporate America.
As exelius mentions, a large part of the demand involves companies that are a little schitzoid and dysfunctional, who have decided it's easier to throw money at the problem and use technology to paper over the cracks.
There's going to be big dysfunctional corporations for decades to come. There's no guarantees in life but investing a little time in a technology like that is probably going to pay for itself and much, much more. I wouldn't do it but I can see why someone would.