Same problems with buying things like antivirus software or even IT management utilities; when they're doing their job, there's no perceivable difference. It's only when shit goes sideways that the value is demonstrated.
Hell you could take this a step further for IT as a whole; if IT is doing their job well, they're invisible. Then they can the entire department, outsource to offsite support, and the business starts hemorrhaging employees and revenue because nobody can get anything done.