I've seen Cambodia's IT infrastructure improve over the last several years, but they still rely on much older, used equipment as their primary source of hardware. The most basic factor is cost. For someone earning about $100 a month (generally considered middle-class and able to reasonably sustain a small family), the prospect of a brand new computer, phone, or other device is unthinkable. Even a PC setup with monitor, UPS, keyboard, and mouse will run you $250. It'll be about 4 years old, but it runs Windows XP or Vista quite well because of lack of service packs. Plus, it's fully loaded with software since the concept of copyright hasn't been fully embraced.
I guess if you could bring low cost, reasonable electronics to the developing world they would embrace it instead of used equipment. I'll let you know when I see it for sale on the streets of Phnom Penh or Siem Reap. For now, it's all used PCs (mostly Dell and HP) and Nokia phones.