Re: Slightly off-topic question
The reason is that for a long time there were very few databases that could scale vertically and horizontally like Oracle did, and the few competitors had no better pricing.
Oracle was able to handle large databases (on high-end servers/mainframes running the like of Solaris, HP-Unix, or some IBM OS) and their data logic when you could not realistically run those workloads on "PCs" - and when "open source" software became available it took years to reach that kind of functionalities (sometimes not yet very well - just look at Postgres partitioning).
If you have large databases which use a lot of PL/SQL code and some of the advanced features, moving away is not easy at all. Unless you can write your own RDBMS like Amazon did.
Remember most RDBMs don't work exactly the same way, and what works flawlessly on X may not work on Y, or not work exactly the same way (transaction management is usually the first issue). You would have to review all the SQL code to ensure it still works on the new RDBMS.
In turn it allowed greed executives to deploy very nasty policies to "maximize shareholder value" - and as less expensive databases can now handle workloads once reserved the the high-end ones, they will get what they deserved for trying to exploit customers so much.
CRM systems are really the realm of legacy nightmares. I've seen some designed to mimic old terminal screens because that was users were accustomed to. Others had to implement procedures and policies that were old as the company itself, and nobody was willingly to change. Add on top of that Andersen/Accenture/etc. consultants telling developers what to do, and you get the picture.