Most health/life insurance have restrictions on what they will cover, especially as it relates to "high risk behavior" like diving. Some 'regular' life insurance policies won't pay out in the event that you die as a result of diving because the policy doesn't cover diving related accidents. Life insurance aside, if you have an accident while diving and need to take a trip in a deco chamber, chances are your current insurance wont cover that either.
The nice thing about dive insurance is that (generally) all of the policies out there (DAN, PADI, DiveAssure, DiveSafe, NAUI, etc...) cover all of these situations and more, including:
Chamber rides, Emergency Evacuation, Any Diving related health problems, Trip insurance, gear insurance for what you have to ditch or gets lost in the event of an accident, etc.
And for less than $100 a year... that's great peace of mind.