PPC got one Major OS release, 10.5 Leopard, and then it was gone. There were PowerPC Macs that were still shipping and came with Leopard in the box and never got a major update. This was back when there were 18 to 24 months between Mac OS X releases though, so it worked out to over three years from announcement I think. But once the MacOS App Store landed in 10.6.8, PowerPC support from developers basically evaporated.
See above. The earliest Intel Macs didn’t have it much better either. The Core Duo and Core Solo based Macs only got Leopard and Snow Leapard because those processors were only 32bit. So only about 3 years for them also. This era of long lived macOS support is very new.