Because he's done so well at that at Oracle
You may laugh, but it is true. Oracle were never going to turn itself into an Open Source company, and give away it's database for free.
Back in 1997, Oracle didn't have any official open source policy. It was not possible to officially run Oracle on Linux. There was a SCO release, and it was possible to grab a couple of SCO libraries and get Oracle running. There was no official project inside Oracle to get the database running on Linux.
Any open source work that was going on at the time was non-official, by individual employees, with no official support by Oracle management. Now, Oracle are paying people to work on the Linux kernel, along with a number of other Linux related open source add-ons.
Wim was an important player in getting Oracle to have an open source policy, and getting an official Linux version of the database, even if they did rip-off Redhat.
For a car analogy, Oracle have delivered an open source sub-compact, and if you were expecting them to deliver a fleet of 18 wheelers, then you're going to be sorely disappointed - but you can't say that they didn't deliver something, which is more than nothing.
It's really difficult to turn around an organization like Oracle, and the amount of open source support, no matter how small, is still more than I would have expected back in 1996.