Why Upload images on other domain - Useful for SEO or not?

[newsnshop]

Why do top sites upload images and css on external domains not on same?

Any SEO specific reason or something else?

[tedster]

When images are served from a different hostname, many browsers will establish more parallel http connections. This means the page can load faster, and there is a small SEO advantage in the extra speed.

Also when a site's server is very busy, the images can be on a different machine and that helps spread the load - another potential speed gain.

[Andem]

This is also an increasing popularity of content delivery networks (CDNs) which also help offset the load and sometimes improve image loading time.