Time4Tea: This is the reason, sadly. Developers could easily put the whole game onto physical media, blue rays, whatever, if they wanted to.
eric5h5: Theoretically most games would fit if they wanted to, but aside from that console games are also not really finished on release anymore just like computer games and require patches.
Time4Tea: Here's the thing - a patch is supposed to be just that: a
patch. I.e. a small file to tweak some portion of the code that needs to be updated to fix some minor bugs.
If the
entire game needs to be re-downloaded, then frankly it wasn't ready to be released in the first place. (that or the devs are being extremely lazy)
Don't mix up patch size and "what does it fix".
Today most games are build up by few but very large single archive files, that do contain the assets (graphics, sound), that are like 90% of a game size, if not more.
There are 2 ways to patch this.
1. swap out the whole archive file
It is the easy way of less resistance and doesn't require much beside a fast internet connection.
2. unpack the archive, change the files that need changes or even swap out code in files and repack the whole thing.
It needs a large amount of temporally disk space, usually much larger then the archive file itself, it needs a good bunch of CPU power for unpacking and repacking and even more importand - it needs a hell of time.
Some games on GoG use such patches and for a good bunch it can be faster to download the whole game again and reinstall it from offline installers, compared to running this type of patch. Depending on your internet connection though.
So, it can be that they only implement small changes, but when there are only a hand full of asset packs and there was a change to each of them...