This example magazine has a number of single page ads with a good bit of copy in them. I'm trying to find an example magazine with those multi-page ads at the moment though.
When I was a child magazines were still very popular and I would not rest until every last millimeter of each one was examined in detail multiple times.
I often think about how so many things now have been optimized (mostly for profit) to the extreme by data-driven processes, with big corporate marketing certainly being one of them.
Up until two or three decades ago, I suspect that it was all based on tradition and the "gut feel" of out-of-touch and arrogant executives talking to each other over drinks (thinking of scenes from Mad Men here).
Yes. Sometimes it was a deliberate tactic - mostly adverts would go for the 'just an evocative picture', but a few would go the 'wall of text' route. My memory pops up the name Alan Sugar for an example of those - really dense walls ...