Because there might be some optimization tricks the author missed, or because the canvas implementation on mobile is bad/unoptimized/doesn't use hardware accelleration? Also, "probability" indicates you didn't even try it.
I did (both Safari and Chrome, iPhone 6), the framerate is definitely low (~10 frames per second?) but it didn't kill it so your statement might be a bit exaggerated. Framerate is a bit lower on Chrome, too.
I did (both Safari and Chrome, iPhone 6), the framerate is definitely low (~10 frames per second?) but it didn't kill it so your statement might be a bit exaggerated. Framerate is a bit lower on Chrome, too.