BES offers a shitload of benefits if you want to use them. Blocking things like the camera or SMS, limiting WiFi connectivity, security configuration, password requirements, etc, on company owned and paid for phones is a requirement for many large enterprises. Additionally, ActiveSync isn't as feature complete with syncing in most cases (Android doesn't do tasks or notes for example), while BES provides complete bi-directional sync between BlackBerrys and Exchange. Remote software management, an always on administrator controlled VPN connection is another benefit.
We had issues with our Exchange server's gateway and it wasn't able to get to the internet, however the tunnel to our location that had BES was up and it had internet connectivity, so our BBs were receiving email communicating what was going on and who was doing what. Sure we could've done that with personal email or with BBM/GTalk, but this way we didn't need to.
BES is a pain in the ass when you don't need any of the above and all you're doing is syncing email, calendar and contacts. But those are all critical features in many places.