A few reasons for me: 1. Google keep messing around with button placement in their UI and it gets irritating after a while. 2. I would never compose a long (imp

A few reasons for me: 1. Google keep messing around with button placement in their UI and it gets irritating after a while. 2. I would never compose a long (important) email in a web browser in case I lost the page. 3. Gmail is one of many accounts that I have and I like a unified inbox.