One reason that I wanted to upgrade to a more powerful phone was to not be left-behind when future O/S upgrades and significant apps (i.e., flash) are released (and will only be supported by the higher-performance phones). The large 4.3 inch display was also a factor.
I'm sure a lot of that is driven by marketing and sales (i.e., to keep phone turnover occurring), but much of it is legit where the new software needs a more powerful platform to run smoothly on.
But I do agree that most apps and functions on a smartphone don't need to be done on a 2GHz 16GB device.
Cheers!