Why 74% dentists don't recommend dental insurance?

Most dentists recommend people to join the discount dental plan, but not the dental insurance ,why?

Here is the reason:

Discount dental plans, designed to provide significant savings on members' dental care needs, have quickly become an attractive alternative to costly dental insurance.
Traditional dental insurance, once the only dental benefit option available, features many drawbacks including costly deductibles, tedious claim forms, long waiting periods and other limitations. On the other hand, discount dental plans are affordable, easy-to-use and free of these hassles.

Insurance Policy:

Maintains monthly premiums in exchange for established benefits
Rarely offered to individuals
Varying annual maximums
Services are out-of-pocket once maximum is met
Deductibles must be met before any benefits are paid
After deductible, co-payment must be met
Orthodontic treatment is rarely covered
Waiting period may be between 6 to 24 months for major services (i.e. crown, bridge, dentures)

Discount Dental Plan:

One low yearly membership fee
Available to individuals, families and groups
No annual limits
No tedious paperwork to submit
Start saving immediately
Orthodontic treatment included in select plans
No health restrictions

source: http://www.foodheal.com/dentalplans/