Perhaps because of the fact that one will have to shell out atleast twice as much as compared to an equivalent AMD richland/trinity based part
Performance dictates the ability to set pricing. I wish Intel's stuff wasn't as expensive as it is, but we must remember when AMD led, we had $300 to $1k+ X2s.
Going back, it is too much of apples/oranges to compare desktop CPU with HUGELY higher CPU performance and higher clock speeds/TDP constraints to a mobile CPU, and only compare GPU performance (which still leads the given example, despite only using the low-end 4600 as the example).
It's just goofy and nonsensical. Nobody is going to cross shop a Richland or especially a Trinity with an i7. That's like someone choosing between a corvette ZR1 and a prius. Oh, the Prius gets 50Mpg, or I can get 600+HP over here. Different products with differing emphasis. AMD has very slow compute by comparison (particularly in mobile), but very good IGP in the IGP world historically. But the conclusions some seem to make are really insane.
Desktop SKU of hugely higher clockspeed/performance uses more power? SHOCKER!
Discrete GPU with dedicated GDDR5 and dedicated cooling is faster than IGP? SHOCKER!
And 128MB of eDRAM is useless compared to even 1GB of GDDR5. Utterly useless. Unless everything you're doing fits in the cache (doubtful), you're still going to hit the shared DDR3, which brings things to a screeching halt in comparison to even a crappy discrete card like 7750/650. Bring a real discrete card like 7850 or 660 to the table and ALL iGPU looks like the garbage-bin stuff it really is for real gaming usage.
Don't get me wrong, improvements in iGPU are always welcome, but the predictions even waaaaaay back when AMD bought ATI, and the Larrabee hype have ALWAYS fallen flat, and nothing is going to change that for the forseeable future. Discrete is a moving target, and if anything, the gap is only growing as time goes by rather than getting closer. All these years later, can any iGPU game as well as even a $100 GPU like a 7770? No. Not really even close.