[Mooff]

they cache jpg/png/gif/css/js ...
and in addition CDNs (content distributation networks) are meant to serve the data via a server which is closest to your location.

Let's say you have a user in canada and one in germany and your server is in england. That's not going to be this fast. But now the CDN has a server in america and one in berlin. The canadian user will be served via the american one and the german one via berlin. -> Speed improvement for both.

That beeing said. We won't use it for the same reason we do not use google analytics. Point is, google will know every single one of your users (via ip, browser settings ...) and can crossreference that to whatever data they want (not saying they will, just saying they can). As this does collide with our data privacy policy and >90% of our users are from germany the gain does not outweight the negative (for us that is).