With all the whining about seats getting crammed together more than ever, is the whining primarily because of people getting larger? Or are the seats truly closer together?

When looking at the major narrow-body jets in service during my early lifetime (707, 727, DC8, 737), it doesn't seem like they had anything but 6 across in the main cabin. Certainly the seats aren't narrower. Pitch may have been played around with, but I don't remember even my earliest flights (I was already about 14) to have anything but cramped pitch.

Was there a time in the era of modern jet service that the Y seating was really any wider? Or are we just bigger, and with crappy service (or none at all) have more time to ponder the sardinity of our inflight existence?