The Diver’s Alert Network is a nonprofit organization
  dedicated to diver health. Its insurance business
  is for profit, and benefits DAN.
Many divers prefer a policy offered by a carrier
  other than DAN, but don’t want to give up access
  to the DAN hotline. The answer: buy the insurance
  policy that serves you and join DAN.  
Under the Hippocratic oath, and by law in many
  places, medical facilities are duty-bound to help persons
  who can’t pay, aren’t insured, or aren’t members
  of an association — as long as it’s a bona fide emergency.
  They are not bound to treat conditions that are not
  life-threatening or do not pose grave risks to health.
  Most likely, they’ll make a referral to another facility.
 Medical hotlines for organization members don’t
  provide hands-on medical care. While they probably
  are bound to help in a true emergency, hotline assistance
  for nonmembers would need to advise the stricken
  individual how to get in touch with the nearest ER
  or hyperbaric facility.  
Many divers who aren’t DAN members have called
  them and gotten good advice or a referral. These
  weren’t emergencies and DAN wasn’t bound to help.
  Nonetheless, they did. If you want to use the hotline,
  but want a policy from another source, your membership
  in DAN would be welcome.