Well, originally they didn't market to kids here. I have some old Playboy magazines (don't judge me) with ads for the NES. I think eventually it became a "family" oriented system after they saw that kids wanted to play and, to be fair, characters like Mario appealed to children. Maybe not DESIGNED for them originally, but the design drew them in.
In the U.S., and some might say this is why so many parents are poor, gaming consoles are a "demand" of children. I'm not going to say if its right or wrong... I mean, again, I've been gaming for as long as I can remember. But I will say that one big reason -might- be Pokemon. What system does it target? Nintendo handhelds. What do kids want? Nintendo handhelds. Would it sell as well as it does without Pokemon? Debatable, but IMHO? Nope.
As for consoles becoming disposable tech? Definitely. While there are GameBoys in museums that have survived the lives of soldiers during the Gulf War (Anyone else remember that god-aweful "I'm proud to be an American" country song? Ick... It still haunts my head with propaganda.), now handheld consoles barely last ten years. Things burn out. BUT... there's kind of a reason? Intricate hardware dies more easily because it's just that. Smaller circuits, smaller parts, and the fact people WANT smaller and smaller hardware. The NES and Atari were advanced for their time, but they were VERY simplistic. Open up your 3DS (actually don't, bad idea). It has really advanced parts, delicate parts. Screens burn out more easily too. The GameBoy didn't have a backlight for example. Now they're LCDs and LEDs and, to be fair, these can burn out.
Cellphones, cameras, smart phones... even PCs. We live in the age of disposable hardware. I don't think companies are so much taking advantage of us, I think it's just the sacrifice we have to make for relatively affordable YET advanced hardware.