Your users, especially when working outside of the office, no longer need to always connect to the corporate network to get work done. They often connect directly to SaaS apps.
Ed is working from a plane, Emily just uploaded that strategy deck to Box, and you’re not exactly sure where Phil is, but you know he’s working based on the number of emails you’ve received from him. Today, this is how the world works. Before, everything was contained within your network perimeter — all of your critical infrastructure, servers, applications, data, and people. (Ah, remember the days of desktop computers?) Branch offices used to backhaul all traffic to corporate, so you could easily extend the scope of your network perimeter. Naturally, your approach to security was different, because the way people worked was different.