Some of the reasons why this trend WILL continue:
1. Critical software like databases needs support. To the point where there should be someone who can come on premise to fix things.
2. We need to use X because X is used by other big corporations and you never get fired for choosing X.
3. The products (Oracle,MS SQL) are not that bad. (Not sure if there is a better way to put this)
I could be wrong, but I can't think of any other important reason. Can anyone pitch in their experience?