rgatl does have a good point about familiarity. Back in the late '90s, ('98/99 time frame) the US Army was using a UNIX based system running on RISC processors. While the system was powerful and capable, it wasn't very well liked. The reason? Because it wasn't Windows based, it had a "windowed" GUI ala Windows 3.11. I heard somebody literally say, "That does not look like Windows." He wasn't the only person to say so. So within a year, the company who designed the system redesigned the entire GUI to match Windows 95/NT 4. THAT was how fast people adopted the Start menu. In less than 5 years after the release of Windows 95/NT 4, the Start menu was so deeply ingrained in society, that the Army decided that a UNIX based system should look like Windows 95/NT 4. Just because it was familiar to most of the Soldiers in the Army at the time.
Familiarity goes a long way when it comes to selling stuff. That is why Microsoft made such a killing in the desktop, laptop, and server OS market.
On a tablet, or a hybrid like the Surface, or a desktop/laptop the Start menu makes more sense. On a phone though, I'm on the fence. I'm not sure it would be that practical. How many of you remember Windows CE? It had a Start menu GUI like its big brother, but didn't take off at the consumer level. It pretty much was used on business oriented devices.