I always wondered about the theory behind it.
I understand why long sales letters "in general" convert better.
(they address all the possible issues the user have etc)
However, I don't understand why many squeeze pages are short.
Why not a long letter for opt-in?
I do know all the "rules" are not absolute and probably there are some long letter type opt-in pages which are doing well, but why "in general" short pages are better?
Thanks for your input in advance.