Because of the long term benefit of the commons approach to reducing their expenditure on technology development by allowing a multitude of other interests to share the cost in the long run. The commons approach also makes it possible to cultivate a larger overall market for services that can be robust to multiple business interests to service a range of customers. Instead of a one vendor defining the produces and services around a tech.. _customers_ shape an array of products and services based on their needs beyond which a single business entity can adequately service.
Whether corporate entity invests strongly into open development or closed development when creating a new technology implementation is very much about the timescales over which they internally assess return on investment for dollars spent. Companies that are short-sighted and looking for instant market advantage without thinking about long term market viability of the technology...will have a very hard time factoring in the benefits to an open development model into their business strategy. And for those companies, I can only suggest they find a new executive team and do a re-assessment.