If you're a tech-savvy startup, then sure, you just put a few guys on staff, but if you are most other kinds of businesses, then you'll employ some 'good-enough' administrators for the day to day operations, but you won't be able to necessarily employ a full team for something that isn't core to your business.
Another common scenario is in government, or large companies. Especially in government, we, as tax-payers, would consider it wasteful if the gov were hiring top notch tech engineers to maintain their file shares and directory servers. They are also completely unwilling to put a system in place with a company that not only will be available for same-day support on critical systems, but will also have to be relatively certain that company will be around in 10 years when they are still running those systems.
In short, support is probably more important than you're giving it credit for, but even for customers where it isn't, RH's credibility has opened the doors for every other Linux distribution and their ability to do work inside the Enterprise.