Why is it important for all health professionals to maintain current
CPR (cardiopulmonary resucitation)certification?

**If you mean health professionals as opposed to no one or as opposed
to other members of society:
  The more people who know CPR, the more likely lives will be saved. 
Health professionals are life savers... who better would the
government require to know CPR?

**If you mean why must they have current certification:
  1) The "best" CPR techniques change fairly frequently.  The powers
that be want CPR to be performed using the newest "best" method.
  2) In an emergency, remembering how to perform CPR might be a
problem.  However if you have learned it several times over the years
then it is more likely to stick with you through any circumstances.

Right off the top of my head I'd guess that it's probably related to
liability  issues.

tutuzdad-ga

Absolutely it's liability issues.  "Techniques" don't change hardly at
all, but the recommended sequence of events varies somewhat from time
to time.  This information may be valuable for those who do not do CPR
regularly, but is not that useful for those who do.

In general, however, CPR classes are worthless (as compared to
frequent experience performing CPR).  As someone who has spent 4 years
as a paramedic and is now a doctor, I can say definitively (if
anecdotally), that good CPR is perfomed by people who have done it a
lot, and bad CPR is performed by people who have little or no
experience doing it on actual patients, regardless of the number of
times they have recertified.