Perhaps most people aren't familiar with the keyboard as much and would much rather have the dedicated numpad for quality of life.
Many gamers would like the numpad since some games require that.
Enthusiasts on the other hand are more familiar with their keyboards and look for aesthetics over functionality, thus making 60% boards and TKL boards more appealing than the oversized 104 key boards which also take up more space than necessary.
Gamers will also want tons of macros and keys because they feel their epeens aren't large enough.
However, most people here don't care about silly macros and instead care more about tiny, pretty looking pieces of plastic.
Just my small take on the subject. There are surely more ways to look at this and more that goes into the appeal of certain form factors.
If I was typing all day in college and wanted a portable or was restricted to a tiny dorm room, I would definitely look into a 65% or 60% rather than some massive IBM 122 behemoth.
Does this mean that most of the enthusiasts are college students? Hmm... I work for a large tech company that hires many grads, and I don't ever remember seeing anybody with a small daily driver at work.
Regarding gamers... I think I may be in the minority. I use macro keys and simple remaps all the time when I game. For example, I'm currently playing Wasteland 2. It's a great game, but the keyboard controls (like many PC games) are spread out across the entire keyboard. L = Logbook, B = Burst Fire, I = Inventory, etc. It's nice to have a dedicated macro pad for some of these controls so that I can bind them in an order that makes sense.
I also used to play a MMO, and I ended up switching to a macro keyboard because I needed the extra keybindable buttons. (I ran a mod that used said buttons to alter the behavior of the mod.)
I dunno what's that
HHKB = Happy Hacking Keyboard
http://www.amazon.com/Happy-Hacking-Keyboard-Professional2-Black/dp/B000EXZ0VC