Let me give you an example(hopefully not a bad one) I use to live in SoCal, there were lots of Western fence lizards. There was not as many but still lots of alligator lizards. And some skinks. But only once in my life did I find a coastal legless lizard out. It was crossing the road.
Now lets think about this. I found these areas with loamy soil that had literally hundreds of Legless lizards. You could lift a piece of tin and see nothing, then sift the soil underneath it and find several under every piece of tin. I could find far more legless lizards, then western fence lizards. Yet, I "saw" far more fence lizards out in the open.
In between was alligator lizards, while I saw lots out on the surface and climbing on plants. I found far more under boards and tin. Then skinks, I did see some out, but weather permitting(cool) I could find lots and lots under cover.
So you have four lizards that are at least locally just as common as eachother, but have different degrees of how much they spend time out in our world.
With legless lizards, its very easy to see they spend most of their time in loose soil, and very little time out in the open.
This same thought applys to monitors. Monitors as a whole, spend very little time out in the open. They as a whole spend lots of time in things. Things like burrows, crevices, hollow trees, etc.
Of course some species spend a fair amount of time out. Many raparian species, ones like Salvators, mertens, niles, panoptes, mitchells, etc Again, its easy to see why they can do this compared to other monitors. They do not have to worry about overheating, they have water to cool them. A desert species cannot do that. Most large desert monitors(lots of mass) cannot change high body temps when theres no way to cool off.
Theres also escaping predators. Raparian species can jump in the water and land predators are outa luck. Or they can run out on land and water predators are outa luck. So they play both.
What I am getting at is lots of these ozzie smaller monitors are land dwellers, they cannot efford to go in the open, as in Oz there are tons of predators. In fact, other monitors are keen on them. So they live in safe places. They do spend a fair amount of time looking out. Sitting at the mouth of burrows, nose sticking out of holes in trees, etc.
Think about this. In captivity monitors mate all the time. Yet are find researchers rarely if ever see them mating. The truth is, millions upon millions bred and lay in any givin area montiors live. Yet they do not see them breed? Why not?
Now consider, when monitors copulate, they do so for hour after hour. At times 24/7 for up to five days. Why are they not see doing this? Thanks