IBM only gave maybe 1.0 shits about gaming, to the extent they needed "business graphics" like charts, and maybe just some extra fun shit. The primary competition was loads of CP/M "business micros" with not many real graphical games at all. IBM benchmarked the Apple II+ with a Z80 Softcard because that was the ultimate mullet machine, all the business software upfront, all the gaming party in the back. CGA was good enough for an Apple II game or a pie chart, and that's all they cared about.