CDN (Content Delivery Network) is a network of computers that hosts files from the servers all around the world. It serves files from the closest server to the visitor to make download process faster. It also allows visitor's browser to download multiple files at the same time. So, the reason of using CDN is speeding up the website.
Your visitors love faster websites more. They don't want to wait a webpage's loading. The search engines award faster websites. Because CDN is faster then hosting files from your server, it helps your ranking in the up direction. We recommend you to use the CDN version of common CSS and Javascript libraries anytime it is possible.
