Maps do not currently reveal an area when you use them, they only put in place the map pins. Ideally, if you buy a map its because you want the area mapped out as well. I know many of the maps I have, I've made of areas where numerous tunnels lead to various areas making it tough to navigate an area with the minimap at all. So it'd help to be able to see the location of the entrance and exit of a tunnel by having the full map revealed when I use it.

This is not done because you can make a map without having, yourself, revealed the entire area. If you want your map to show the entrance and exit of a tunnel, mark those points as such on the map when you create it. Otherwise, they won't be on the map that you produce.

I have already.

Trouble being, I can't walk into an area and remember "where" the tunnel is or use the map to find it. Instead, I have to walk all over until I locate it again. I can always make due I suppose if there is no work around to the area being entirely revealed only if you've really explored it to map it.

The only thing is you could bodge it with a grid of triggers which counted the area explored on a single area and if it was 80% of the total, then you'd be able to map (reveal all) the area. Problem is, this just mess up areas with lots of huge triggers, add server load and various other things, but it could work.