As a general restorative dentist this is a daily mantra of our patient base.  It's a difficult question to answer on several levels.  First off, dental insurance truely is not insurance- it's a cash benefit provided by an employer, so we usually refer to "insurance" as "benefits". 
Another misconseption is that benefits cover all procedures completely.  We try our best to explain the extreme varaiations in coverage for all given benefit providers (insurance companies).  Most patients generally have no idea of issues like deductablety, co-pay and of course plan limitations (non coverage and exclusions of coverage). 
Years ago, I had an intersting conversation with my brother-in-law regarding insurance plans(he's in the business).  He refered to insurance policies as a " product".  On further reflection thats exactly what insurance benefits are; products.  Someone makes them (insurance companies), someone buys them (employers), and someone uses them (employees)  Just like any product, there are good ones, bad ones, and in general you get what you pay for.  Deciding on the product is up to the purchser (employer). Usually dental benefits are "tacked on" with a medical policy- like garnish, since this constitutes the vast majority of employer premium dollars.  Some where I've read that $0.50 is spent on dental for every $10 for medical benefits 1:20.
However, if employers really wanted to help their emploies make best use of their benefit dollars there is a better way.  It is know as Direct Reimbursment.  More on that next time.