I would argue that the foam is used inplace of honeycomb for puncture resistance.  Try taking a sharp object and stick it into foam and there isn't a huge difference.  What would be better is balsa core for impacts such as rocks, high heels and tools being dropped.  Ironically, this may be worse for the structure since balsa is so strong in compression, it will "telegraph" an impact to the far side whereas foam and honeycomb doesn't.  A hammer blow to a blasa maniate can be seen on the backside where the round detail of the head of the hammer is outlined.  Un-crosslinked PVC core (Airex) is even better at protecting laminates than crosslinked PVC (Divinycell and Klegecell) since it is more flexible and almost impossible to destroy by impact.  It unfortunately will creep under sustained laod and gets soft when heated so it's unsuitable for thin skinned structures.

 

We did a composite analysis for Randy Smythe, an Olympic Gold medal winner, awhile back for his 20' day sailing catamaran to race in the Worrell 1000 (1000 miles of open ocean sailing from Virginia beach to Florida in 5 or 6 stops).  Unfortunately, the Divinycell core we spec'd was substituted with Airex somewhere along the way.  Around the second or third day, the leeward hull collapsed at a crossbeam due to sustained load causing the inside of the hull core at that point to copress, becomign thinner, causing a reduction in the section modulus and ultimately collapsing.  So EVERYTHING comes at a price!

 

Dan