Why? It's one thing building a custom designed ARM SoC. It's a whole other ball game competing with Intel. Intel chips are great, can't see how Apple could do better.
Good job I got a free 3 year warranty with mine from Apple

. So far though I have thoroughly abused my 750M and it's not gone wrong once.
Can't see it, AMD chips are good but they are definitely not efficient, that's one where Nvidia has nailed the market. Maxwell is a staggeringly efficient GPU, I'm just praying to the big fat sky fairy that they include something like an 850M in the Broadwell update.