Based on some similar experiences with a corporate client:
- Purchasing-level decisions have to be approved by someone who worries less about the money being spent now than the situation the company will be in later. In other words, if I offer a free alternative to expensive commercial software, they'll be concerned that even though they'll save a few hundred or thousand dollars now, they'll be hamstrung if I ever leave, or if the free software vanishes.
- These decisions are also often made by individuals who are not all that technically inclined, so they're suspicious of what they see as "amateur" versus "professional" (or commercial, or enterprise) software.
- They're concerned about compatibility with their business partners.
- They find many of the things that we like about the representation of free or open source software -- names like "Mozilla", "Firefox", "Thunderbird", "Foxit Reader", the FreeBSD daemon -- to be amateurish and annoying.
Yes, that leaves the door wide open for startups. However, there's a reason why this tends to be the pattern as businesses go from "startup" to "enterprise".