Safari doesn't support WebGL either because of security issues (AFAIK only Firefox does) so while it might be easier it wouldn't work.

Safari does support WebGL, but it's off by default. You have to enable it in the Develop menu.

chrome supports it too, which is higher than safari in use. firefox + chrome covers more together than any other 2 browsers in combination doesn't it?

but I see what you mean about compatibility, with canvas they get ie9 + firefox + chrome + safari, almost everything for desktops.

They could have supported WebGL for better performance on browsers which support it with a fallback to Canvas 2D for IE9. But I'm sure Microsoft didn't want them to have it running faster on other browsers :)

All modern browsers support WebGL: http://caniuse.com/#search=webgl