Because they shaft people
I've worked for several IT firms, in the City running an IT department, supplied secure networks to HM Treasury and at various times been a full time journalist dealing with many types of vendors.
Not one of the firms I have dealt with is anywhere near as bad as Oracle.
But I got my last job because of Oracle.
I was working as a contract project manager on a trading system. Short version is that they had shafted the group head of IT big time (he shortly became the ex-head and no it was not coincidence).
I didn't know this, but I did know that Oracle felt they were on a role with my bank and demanded more for the licences than we had budgeted for the entire project, including development, hardware and a wide area network connecting all the major banks securely.
I rejected their pricing so they went to the board to screw me over.
Ironically this did me no end of good, they didn't know who the hell this "Dominic" person was but anyone who could make an Oracle rep froth at the mouth was good in their book, so I got "head of IT" business cards soon after.
This is not an isolated story, my advice is to never ever let an Oracle rep into your building and do not trust their promises about the price of support either.