Here's an example. Was talking to one of the new members of the College of Winterhold, the Nord. Told me he made a bad trade with Enthir and wanted my help. I talked to Enthir and he said he'll fix the situation if I go fetch him his staff. All he said was that he sold it to the wrong person - he did not tell me who this person was, or where I could find him. I figured it might be the Dark Elf in the Jarl's house, because that guy asked me to get him a staff to help him keep up appearances, and I said no - so maybe he went looking somewhere else. But nope, wasn't him. So I went back to the College and talked to every [censored] NPC. Nobody had any relevant dialogue options. So I went to the few places in the city of Winterhold that had people in them and talked to every [censored] NPC. Again, nobody had any relevant dialogue options. At this point I was absolutely exasperated, so I decided to turn on the quest marker. Turns out the guy was half-way across the map, North of Falkreath. Apparently, I supposed to [censored] divine his location...
This is only one example of many. I can give you so many more examples where you're basically [censored] if you don't use the marker.
I don't see a problem with that. Eventually, someday, you would end up North of Falkreath and find the location of this person. Yes, it may take you months of game-play, but eventually you would find the right place. That just makes it all the more epic.