Because you would be either dead or immortal by the time you reach attnam

I've always felt IVAN was characterized by the dungeons with their mix of random enemies and design as well as static additions that presented new problems or possibly new solutions (though certainly not without cost). Random encounters out in the wilderness I feel would break the feel of that and since the 'real' part of the game takes place in the dungeons anyway, I don't think it would be a positive change. Also worth noting is that as the game is at the moment, the previous concern is irrelevant because the longest trip anywhere in the overworld is from the underwater tunnel to Attnam, and as the second longest trip is generally much smaller, unless you make random encounters really common there probably won't be all that many and thus it won't be able to make the kind of impression they do in ADOM. Though, really for me it seems like it will be more annoying and unfun than otherwise to have random encounters.

IDK, you could try to reinvent the random encounter model, instead of just the "you are ambushed by a bunch of random monsters" model, give you random encounters that give you a chance to add alignemtn roleplay "you encounter a carvan of traders, do you want ot help/pillage them" or such. I think it could be a tool to really flesh out the IVAN world.

I dont disagree that some aspects of random encounters are pretty lame and dont really add much to a game, but as it stands the overworld has no real purpose. you could just as easily eliminate it alltogether. All it does is occasionally starve a beginner player.

The latest version of the game is 0.50. The plan was that there'd be a empires and cities out there doing trade, wars, politics and other sorts of things without the player doing anything about it. This game is not finished, therefore some things that seemingly have no purpose, might simply not been finished yet.

The more we talk about this the sadder I am that they stopped development at 0.50

Aren't we all, though?

There really needs to be a warning on a locked door if it's Merka's. It was such a promising character too...

A scatterbrained wand. Does the effect of a random wand when zapped. Has a chance to break itself resulting in a random effect too.

And probably an outlandish idea: The Room of Change Material. A simple non-descript room that looks no different to the others on the level, but anything inside the room occasionally changes material to something random. Upon entering the room there should be some sort of alert, like "This room seems dangerous", "you get the feeling it is not safe here", "Your skin seems to be crawling". The change should affect all bodyparts along with inventory items, but only has a chance to (to prevent everything changing at once) and without an announcement of having done so. The message "Your head suddenly feels like marble!" would definately give it away.
To make things more interesting, there should be a unique monster that spawns in there, and is slow-moving so it has time to get its limbs and such changed. A golem of some sort, perhaps?