I have a theory that's based on no actual facts but sounds nice and is similar to what you're saying. When the 1E books came out there were two types of people. One were kids that were ages 9-13 (see the poll on ages if you don't believe me). Those kids probably had a copy of the Basic set (Holmes or later Red Booklet) and piece-wise incorporated ADnD rules into their game. The other type of DnD'er was an old-schooler who learned DND from the ODnD booklets, had probably worked out their own house systems for some aspects combat, and adapted (like the kids) the ADnD rules to their existing game as appropriate - grabbing the cool stuff first ("hey, different weapons do different damage").