Somewhat anecdotal but nonetheless you may find interesting. Aside from a few remnants of my tomato box O O collection, my collection today consists of 4 or 5 private collections leaning more towards the CA/MA. Each of these were compiled by collectors who shopped primarily at comic shops and not newsstand retailers and are representative of their buying habits, with only occasional newsstand purchases (probably when traveling.)
I believe that this may be reflective of most CA (and later) collections, whereas full or partial newsstand collections are much fewer in number due to local geography or inconsistent buying habits.