Exploration means different things to different people.Not as much as you might think. To the original dungeon occupants they'd have just been ordinary doors - they're only a problem for silly adventurers who can't find them later.
That, and they play right into the exploration side of things.
Not saying you specifically do this, but it's interesting that people don't like secret doors, don't like mapping, don't like frustration in general - and then complain the exploration pillar has nothing in it.
You seem to have a very old school dungeon crawl style. That's great if it's what you and your players want. A lot of people just have a different style which is more ... well I'm not sure how to describe it. Realistic isn't exactly right. Plot based is only part of it and not necessarily accurate.
People want locations to be part of a bigger story? Maybe?
In my campaigns, location and dungeons are never the focus, they're the set dressing. So yes, there's exploration but it's more exploration of mysteries.
Which I'm doing a crap job of explaining because all I can think is "not old school D&D".
