I kind of get why it was buried, it came out a full two and a half years after the Macintosh was released, and basically three and a half years after the Lisa, which was itself arguably the same development track as the later Macintosh. It was also given a skinned GUI that looked a lot like the Macintosh Finder. There had also been several product iterations beyond the original Lisa and Macintosh that added external hard disk support and other useful features.
The only places I've seen Apple IIGS computers "in the wild" were when I was a kid in school. I expect that this was partly to allow the school district to continue using the educational/edutainment software that it had invested-in for the prior Apple II models. After all, the original Apple II debuted in 1977 and the IIGS the better part of a decade later in late 1986, and was produced until something like 1993. An organization that had a ton of software from their late-seventies or early-eighties Apple II computers might want to buy more Apple II models as legacy products. Even if there were some additional advances in the platform itself, the company behind that platform had already started to move on, and likely saw the Apple II line as having few development paths left going forward while still maintaining backward compatibility.
We saw the same sort of thing when Jobs returned to Apple and brought the legacy of NeXT with him, but because computer hardware had managed to become a lot more commoditized, general purpose, it was not as much a hardware issue as a software/OS issue. They maintained a virtual machine environment to run classic System within OSX to again allow those with investments in software for System to be able to continue using it (and to allow it to be used when there wasn't a version written for OSX specifically yet) but they certainly weren't looking to perpetuate the original Macintosh line once the models running OSX had supplanted them.
Don't mistake me, I'm not one to particularly celebrate Steve Jobs, and I've never been an Apple fanboy either, but it's not surprising that a company would discontinue one product line, even one that had been successful, when another product line with a lot more potential has come out and seen widespread adoption.