As the titles say. Small patch installers are only available for Windows, the other OSes need to download a new installer. While for most games that's not too much of an issue, there are games with installers that are more than 10G in size. So why are there no patch installers for Mac and Linux?

Because they hate mac and linux?

Because their installer is 10+ years out of date for Mac & Linux?

I don't think it is a deliberate thing, especially by GOG, and in reality it is just like the lesser support for Linux and MC games here, where you get fewer. I certainly have patch files for a good number of Linux versions of games here.

Really, there are many Windows version games here that have the same issue, where they only provide a full installer update and not a patch.

Blame the DEVs or PUBs.

What in the world are you even talking about? There's no GOG installer for Macs, it's essentially a tarball which uses the system installer. It's literally impossible to be "out of date". They don't do patch files because they just haven't bothered.

Because a self-applying diff is so hard to code (sarcasm). As others said, most likely due to a lack of interest.

They actually used to use disk images for Mac downloads, which in many ways is better than an installer; you just open it and drag the game to wherever. There's no chance of files being spewed all over the place (not that Mac games need random system libraries and crap installed anyway). However that does make it impossible to do patches. They switched to a package/installer system some years ago, which could do patches, but then they didn't bother.

I have created a very fast very good diff identifier to delete identical files between two directories, including duplicates. As long as you aren't working with 100Mb files that change very slightly or huge files like 4Gb Pak files then this would be fine.

That's really not difficult to do, I agree. Just a bit of scripting and for large PAK files you can try xdelta to create a binary diff. I once did a test with 2 installers for the game SOMA. The installers were about 10G in size but the archive containing changed files and binary diffs was only like 100M if not less. It's also a bit annoying that for Windows the installer archive files are split at 4G while on Mac and Linux they aren't. Probably to support ancient file systems.

Because GOG loves paying the the server bandwidth every time someone has to download a 30GB+ Linux installer every time game devs apply tiny sometimes less that 1mb patches, with early access games that receive more that 1 patch a week it can be 300gb+ of downloads a month just to keep 1 game updated.

I feel sorry for the users with monthly data limits due to greedy ISPs.