Probably because APU's are getting better and more pc gamers are doing handhelds and apu laptops instead of dedicated desktops. PC gaming has gotten really expensive.

This is a non comparison for at least the next 5 years. A dedicated gpu is still a better choice hands down for gaming. Even going on a lower end build an older gpu will still beat the current best apu by a good amount, but in 10 years time it may not be so necessary to need a gpu over an apu. GPUs are getting too power hungry and expensive. Gamers gonna game, but they won't all want to spend an ever increasing amount of money to get better graphics, and arc would need at least another 5 years to be competition enough to claim a worthwhile market share from amd or nvidia and that's wishful thinking. Long time to bleed money on a maybe.