Time is money. No doubt about that. The more time your customer waits for your service response the less coins may hit your pocket. You may ask: why? If your page loading is too slow your "almost" customer hits back in his browser and selects another link from sponsored links Google provides him. You loose this customer in favour of another supplier.
What about Google? Was their service (no kidding, it is a sevrice that searches information, paid by ads) always so blazingly fast? Let's check this site performance monitored from London server over few years:
In order to double check our measurement results there are monitor result from Newark, USA: