Yes, our customers do buy support contracts, and almost all do not go for the standard package but customized ones tailored for each business need. Some only need 24/7 phone incident support in case stuff hits the fan and other might need more hand-holding when it comes performance tuning, configuration, and just regular 8/5 phone support.
When something goes wrong, there are usually two classes of need. Those that can wait 48+ hours for a real-fix, or those that need it there and then. For some of our customers, 24-48 hours is an eternity and a single incident would've saved them the cost several times of the support/license versus not having 24/7 insurance.
It basically comes to do your needs, we customize our support plan for each case.