3d not being required makes a hell a lot of sense and of course it wasn’t people have been drafting on paper for ages. They might’ve ended up on Mac or maybe Amiga, but an SGI workstation is quite an investment when you don’t even need to spin polygons. IRIS GL dates back to the early 80s, doesn’t seem so much to be a timeline but price and need thing.

There apparently was an IRIX version at one time but with no user base preference, more likely they were thinking “where’s my C: drive” so once 3d acceleration hit the mainstream everyone happily switched back to Microsoft.