its definitely necessary.. latency is a factor of distance. No matter how big the pipes, the speed is always limited by the speed of light. With one web page having typically 50 connections to render it, a CDN service will always help improve web site performance for users around the world.
Your argument was correct before video became common all over the internet...............all that video needs help moving around. If you're just talking about sending a simple e-mail it doesn't matter.
Video is buried in every corner of the internet today. Having Akamai service is mission critical for anyone managing a hyper connected work force. The cloud is getting more important every day.