For big commercial companies there is an additional reason.
When a big company (10.000+) implements a product "company wide" they spend quite some money (5 figures at least; probably 6 figures). Making installation package; updating internal databases; changing processes; training people; doing data migration; building support site.
When you do this investment you want to have "some sort of control" on the product so you know your investment is not lost.
This is something Open source proved not to deliver. There have been plenty of good open source product where only a shadow of itself remained in a short time; simply because a better open source product appeared (with my background I think about cvs -> subversion -> git).
The people in the 2 communities do not care about data/process migration.
As a big company with a company wide usage of this tool you are faced with following questions: Are there tools to migrate your 1billion documents to the better tool? (Very unlikely.) How much will it cost to train your people to learn the new tool? (well again at least 5 figures) How much will it cost to continue development of the tool yourself? (Didn't we make the developers redundant as we implemented this great tool?)
I'm not saying that these risks do not exist with commercial tools. The risks are only higher. It is up to the company to decide which risks they take and which they want to avoid.
Greetings from Belgium
Jantje