The main reason I'd see for originally including PNG color space metadata is to correct for the inconsistent gamma between OS X 10.5 and earlier (gamma 1.8) and

The main reason I'd see for originally including PNG color space metadata is to correct for the inconsistent gamma between OS X 10.5 and earlier (gamma 1.8) and Windows (gamma 2.2). Snow Leopard and Lion have switched to 2.2 so the problem is graduating, but web designers before 2009 had to worry that the colors on their Macs did not match the colors on PCs. The real question is why throw in the whole 100K including the color space and all, when only a gamma value would suffice?