As a pirate, usually, i deal with iso images elsewhere. But why on GoG? Their system is simply awesome. It is quick, simple, easy, doesn't require any knowledge (or third party programs like daemon tools) plus it is... GoG!

Bear in mind that ISO conversion bears risks and can damage your program/game etc. Especially if the game you want to turn into ISOs has DRM or other nasty programs integrated in it. Example:

The pirated, ISO image of Vampire Bloodlines, compared to the retail original i own, has many faults. Absence of sounds and sound effects, in various occasions, faulty animations (more than usual) and other things, proved to me that either the iso converter wasn't skilled, or the conversion had been faulty due to aforementioned programs' inclusion.

GoG is pretty nice as is. You don't need iso images. Also, most games here are uncensored and/or collector/goty/complete packages anyway. There is absolutely zero reason for a request like this.

EDIT: actually, never mind.

GOG updated Overseer to the DVD version nearly 2 years ago IIRC.

Unless you mean something else?

If you want to play an older game on a newer machine, then the disc images wouldn't provide any additional benefit, and may even include a lot more headaches. But if you want to play the game on a period relevant machine (a PIII Win 98 one with a VooDoo4 card for example), the current GOG installer will prove more of a headache than having an ISO to burn to a disc (or mount on a virtual drive).

So main benefit would be for those willing to play the games on a retro PC.
It doesn't, unless you mean damage in the same way that ripping a CD to MP3 damages the audio. ISO is not a 1:1 copy of the disc, it's just a copy of the filesystem of one track (so hybrid discs will be missing half the data) that ignores any extra data on the disc, like audio tracks, files at specific sectors or sectors marked as bad. To copy those you need another format, be it BIN/CUE for audio tracks or CCD/IMG and/or MDS/MDF for true 1:1 copies.
That is why most scene releases had them as BIN/CUE with a crack included, or CCD/IMG and/or MDS/MDF for a clone, regardless of the inclusion or absence of any DRM.

While preservation of the originals would be an important goal, iso images are not that by a long shot and would be just a waste of effort. bin/cue would be a lot closer, but even that would probably miss things. I don't know if there even are good formats that would preserve everything - and even if so, actual preservation would rest better on the shoulders of individuals genuinely interested in such a thing and knowledgeable in all the details that it entails, not companies trying to make some money selling games.

That being said, GOG.com could improve some of its offerings towards that goal. I'm always perfectly happy if there are no important omissions (like dos setup utilities), encryption to keep it away from me (passworded installers) or lossy compression that degrades it (cd audio tracks in mp3 or ogg format), but it's not uncommon that there is something that irks me.

For instance, it would be really nice if GOG.com shipped the DOS executables and setup utilities for games even when they decide to go with scummvm. It would take neglible extra space, not weeding out the extra files would actually save work, and those not interested in them would never even know that they are there. If a DOS game misses its setup utility that can be a pain, but as long as it's somewhere on the bin/cue image included primarily for the music tracks, I'm fine. I don't need it served on a silver platter. Any CD audio at all I would totally want losslessly compressed, but iso images? No, just gather all the original data and it will be fine.

You need softwares like daemons tool to mount an ISO image and some DRM in-game detect them to block the games (the retail version of Fallout 3 for example). So, an ISO is not a good alternative.

No I didn't know that. I must have missed that update. Thanks for the heads up.

Windows 8 has native ISO mounting support, for XP, Vista and/or 7 grab this file directly from Microsoft. Linux and Mac should both handle ISOs natively.
As said before, ISOs are not 1:1 copies though, so some disc checks will fail, and any extra information (like audio tracks) will not be there.

Ah, I didn't know that, thanks !