Customer willingness to overlook standards violations, it turns out, is often proportional to the investment a customer has made with a particular vendor. And, given the chance, vendors will almost always seek a competitive advantage by bending standards rules.
As a technology, open systems storage has yet to match the standards compliance and interoperability expectations of open systems networking, and in fact may never match it. In the IP and Ethernet world, standards compliance and interoperability are simply assumed. No one would think of introducing a new Ethernet switch or network interface card (NIC) that did not fully comply with all the relevant IEEE, IETF, or ANSI standards. And no one (with, perhaps, the exception of a Cisco) would presume to impose a proprietary protocol on the market and expect everyone else to simply follow along.
Even today, we continue to have both vendor-specific and "open systems" functionality living side by side. When building SAN fabrics, proprietary expansion (E_Port) modes tend to have richer zoning functionality, compared to the open systems mode. Customers are not so committed to open systems that they will sacrifice vendor value-added features, and yet often complain when they run into switch interoperability issues because of them.