In the context of macOS, shipping out even a 75MB bundle of trusted certificates is "not significant". Bundling it into the browser would increase the download

In the context of macOS, shipping out even a 75MB bundle of trusted certificates is "not significant". Bundling it into the browser would increase the download size by a substantial percentage, but 75MB as a 'security update' distributed through the App Store is comparatively tiny versus the 1GB+ which is typical for 10.11 to 10.11.1 style updates.