It's simple to use, easy to setup, it doesn't have any unnecessary features other than voicemails that I need. There is no way for me to know if someone has called my cell phone when they leave a message or not unless its checked in some kind of queue somewhere else - which can be time consuming as well. If you are looking for an all-inclusive service without having to worry about anything but your messages then this might work fine with you.
The simplicity allows users to focus less on things