MB: "Do you want to ask about why the shift away from dungeon-crawls and to more variety in adventures, or insult people who play computer games?"
Oh, that must be it

!
Mate, I play computer games, always have...always will

...and no, I'm not insulting anyone...just stating an obvious trend in computer games over the last decade, one of increasing options. Anyhow, I never said there were NO modules set above ground, or investigative in nature, only that the majority were not **so 1E appears on the surface to be different then 3E in this way** and that mate, is the topic of this thread "How have dungeons changed in D&D".
One thing to consider is that above ground adventuring can be v. similar to delving. Think about it, moving through rooms in a building, or down narrow confined alley ways and streets, forest trails, ravines and the like. So perhaps the "dungeon crawl" still exists in a way, just presented in a different fashion. The "board" is still there, but you can move around it with more freedom.
As far as 1E modules go, I think the topside parts were left undeveloped on purpose, to allow the DM and players interacting to create the story of whats going on (who they talk to, how they get to point A to B, what wacky adventures they have on the way...that all develops "in game", it wasn't usually written down. I remember exploring Homlet and taking days (in game time) checking out other places in and around the village, as the DM made up stuff on the spot...some of which were just as cool as the module itself.
The plots you saw in 2E and later in 3E seemed to keep the players from drifting off into their own thing, and over almost explain too much.
Roth: "Your implied recollections, doing mostly dungeons, are at odds with my memory of play in the 70s. When I was a young adventurer we had to walk 20 leagues through the snow to get to the dungeon, fightin' the whole way. In game time we certainly spent more time adventuing, tracking, scouting, questioning locals for adventures, treasure and information to help us survive the dugeons, etc. than in the dungeon. "
Agreed, and thats what we did as well. The difference I'm noting is the actual module. For instance, if you take a look at White Plume Mnt. its only a half page of intro, yet when we first played it, we spent days (real time) getting to the dungeon area. And the trip was as fun as the dungeon itself!

But note, the DM and players came up with all that "story line" it wasn't written down or suggested (as it often is 3E modules, in plot, ecological and anthropological descriptions, DM notes, etc. So, yeah, I agree with you. In 1E, the details are in the dungeon, but still a majority of game play can occure outside of it, depending on what the players do.