The "90% of users only need [...]" fallacy

Lots of people defend devices with limited functionality by saying "90% of users only need a web browser to check Facebook and email", or something similar. This seemingly relegates devices with lots of functionality to a niche.

This defense is flawed because most consumers already own something that performs these basic tasks. New devices must either (1) perform these same tasks significantly better, or (2) offer new functionality.

What would improve your life more at the margin: a higher resolution laptop to browse the web? A tablet that weighs 30 grams less? Or a Windows 8 hybrid that offers a fundamentally new computing interface?