RandomGal: The 90's versions were compatible with Mac System 7. So, you have to have one of the Classic OSes (7, 8, maybe 9), then you have to run it in an emulator, which is unreliable, plus there are other files you need to hunt down to make everything work at least semi-properly. I'm by no means an expert, but I have the old Mac versions of these games and had looked into how to get them to run and eventually gave up. They might run on one of the OSes that still support Classic (10.4 or lower), but unsure on that.
The point is, in order for GOG to offer the Mac versions, they'd have to actually work, which is a long shot and then there are the licensing issues with Apple in order to be allowed to emulate. No surprise that the Mac versions aren't here.
You can get the os directly form the apple servers, the problem is that you need the old firmware files to use emulators like Basilisk 2 or Sheepshaver. And the firmware files (roms) are not allowed to share, to be on the legal site you need your own old mac to extract them.
The only solution here is what has GOG done already before - use wine and the windows version.