Is standardization important?
Do you want to use practices that are shared in your industry/profession?
If you have invested in an XML publishing solution, you will know the many months of development required to get approval on content models and precise document type definitions (DTDs and Schemas). These are then followed by as many or more months working with designers to turn the allowed elements into deliverable content (XSLTs).
The DITA Open Toolkit transforms DITA content (maps and
topics) into publishing deliverable formats for web (XHTML), print
(PDF), and Help (CHM and Eclipse).
If you have not invested in an XML publishing solution, it is probably because you can see how costly XML development really is. So a hidden return on investment in DITA is the real savings you get by leveraging an industry standard instead of developing a proprietary one.
When expensive consultants or in-house schema developers of custom XML are no longer valued, they will likely become support people who know DITA's simplified XML and its standard information types.
When you do invest money, it will be to develop your own custom styling or your own specialized DITA Topics and Domains.
Specialization is the answer to those who say DITA's "one-size-fits-all" collection of DTDs and schemas will not fit your organization's requirements and business case.
Specialization allows you to modify those DTDs and enhance the accompanying XSLT needed to present the modified material exactly as you require.
But notice the great savings. By starting with an industry standard, you only pay for schema and XSLT development to the extent that you really need different functionality or look and feel. You leverage all the investment in the DITA standard information types, because your specializations inherit them.
And if you follow the specialization guidelines exactly, you know that your DITA content can be exported to systems that know nothing about your specialization and it will be processed without error.