You're right that the ideal situation is to always have the most current version of the server software installed; however, some of us work with organizations and customers that have outdated hardware and software and we must use what is available.

We do not always have the option of telling our clients they must use the latest server software version or we cannot work on their project. Most of my clients are set with what they have and the timeframes and budget constraints prohibit any server software upgrades.

To maintain my client list, I must be fluent in several server types including MySQL, Oracle, MS SQL Server, and even Teradata. My clients cannot easily change their server types or versions without it being a major undertaking. Besides, there's a lot of debate out there as to which server software is better and I'm not going to start debating that with my clients.

I make more money ($/hour wise) when I work with small companies that are using older software than I do with large enterprises that have the most up-to-date versions. The smaller companies don't have the budget dollars to keep upgrading their software nor do they have the money to keep a DBA on staff. So, when one is needed, they pay top dollar for services. Larger companies keep DBA's on staff with an annual salary and that's significantly less pay.