it's probably more this:
than this:
what i need in a mobile browser was never less than i needed on my desktop. i need all the function plus the ability to, say, tell the browser to request the mobile stylesheet rather than the standard one. (neither microb nor fennec do this.) - you know, i don't browse differently (or go to different sites) only because i'm on the train rather than in my office. i don't switch personalities according to where i am.

the "intended audience"-theory seems more logical to me: probably those who are content with fennec would also use it on a desktop.