One of the things I get to do a lot of is look at IT estates that are a complete and utter mess. Systems overlap in functionality, are difficult to maintain and the links between them are more complicated than Glenn Beck's issues with reality. When doing a Business Service Architecture it becomes clear that the big issue here is that IT doesn't learn the lesson of Unix Do one thing and do it well. In SOA, particularly business driven SOA this is the whole point of services, they do one thing and they are designed to be integrated.
Having the "services" as clean though is pointless if what you have under the covers is just the same old crud with some REST or WS-* lipstick on top, you actually have to have an implementation that is clean all the way down or you are still screwed.
The BSB Specification was based around that principle of doing one thing well, and the whole point of the DSB/BSB split is to keep it simple.
This then becomes the real issue, its actually really hard to architect and deliver simply. In the MDM space for instance you see MDM solutions that morph into MDM + ODS + Reference Data Management solutions. "clean" ERP installations are destroyed by customisation and the Java solution gets some crufty bolt ons because "it was easier to do it there". The delivery builds the blob with lipstick on it and suddenly we are no better off.
Why does this happen? Well more and more I believe its because the SIMPLE pictures that describe a business architecture are either not drawn at all or are abandoned because of their simplicity. People, architects especially, don't like putting in place the rigour and control that is required to deliver a simple solution, its much easier to deliver a blob and let people cope with it in support. Simplicity isn't a valued commodity because it doesn't allow people to show off their understanding of complexity.
"Je N'ai fait celle-ci plus longue que parceque je n'ai pas eu le loisir de la faire plus courte.
--I have only made this letter rather long because I have not had time to make it shorter."
Pascal. Lettres provinciales, 16, Dec.14,1656. Cassell's Book of Quotations, London,1912. P.718.
Simplicity takes time and effort and the end result is much more satisfying, easier to explain, easier to maintain and easier to use. Most people however take the easy route to complexity.