For example which camps?
Mesorah and Kaylie for certain and I believe Morasha as well. There may be others too, but these are the ones that I remember hearing about.
The camps were getting hundreds of packages a day and they needed to inspect each one to make sure that there were no food allergens (nuts, sesame, etc) and then get the rather large and heavy boxes out to the bunks.
I think this is already the 3rd summer that they are banning packages which are not pre-approved.