First because actually not their employees but the customers are their greatest asset, and second, because they can up the quality of what they offer to the maximum so customers are not forced to buy the product and at the same time to curse the company for the price.
When giving higher quality, they will still improve over generations, and will look better in our eyes. The standard itself will be higher.
Discrete boards sold to enthusiasts are a drop in the bucket. The vast majority of sales are to OEMs who pretty much demand a new product every holiday season, and the people who buy an OEM system are more often than not buying a whole system rather than a mix and match set of components.
Theoretically, both companies could put out their most cutting edge products - but once you start, ANY slip in timetable brings criticism, and ANY part failing to measure up to any perceived metric previously reached will start getting the haters out in force. 4K is barely relevant as a statistic in usage, yet a significant portion of forum users across the net are whining and moaning about the lack of 5K and 8K support.
Give the consumer what they want and they just want more, and as for tech "enthusiasts", I've yet to meet any significant number that are content with ANY aspect of technology. You'd be hard pressed to find a bigger bunch of self entitled ramblers anywhere. Give people a 150W card that does the job of a 250W card from the previous generation and they'll whine that it should be sub-30W and passive, give people HDMI 2.0 and they'll whine about (possibly) no DisplayPort 1.3 connectivity... or the card not being single slot, not shiny enough, not the right colour, not quiet enough, not cool enough, too big, too small (Hey! that doesn't look like a premium card!), not enough accessories they'll never use anyway - the list is endless. Like it or not, multi-billion dollar companies don't cater to a miniscule percentage of the market, especially one that will never be satisfied. You could provide a card that is butter smooth on a demanding title at 4K with 8 x SSAA/DoF/motion blur/HDAO applied, and the first thing out of a lot of peoples mouths would be a complaint that the company had previously been holding back, or the driver package is too large, or the software utilities aren't meaningful enough, or most likely - that the company cheated you because you can't push 2 volts through it.
It's been this way for a while. The number of people of confuse "tech enthusiast" with "hyper-critical user with unrealistic expectations" seems to grow larger every product cycle. Intel could no doubt transform their 18-core E5-2699v3 into a desktop part, but how would they continue to keep topping something like that? The moment they slip up and "only" produce a 30-core next time around you have a bunch of people complaining because the rate of progress isn't to their satisfaction - basically back to square one. Sometimes, you just have to apply real world values rather than a wish list - businesses are about sustainability. and they'd soon go out of business if they had to come up with a new process node every year and offer cards for relative peanuts when they have to fork out $7+K per wafer.
Normal, how do you expect sales to climb after what I'm telling you. Customers are not happy and it will get worse.
The major reason discrete board sales are down is because of iGP's. Not everyone games, and of those who do, a fair percentage are casual or playing some inane flash PoS. Once upon a time integrated graphics were just a method for OEMs to cheap out on finding away to display video. That isn't really the case anymore when the vast majority of desktop processors include graphics - that is why sales are falling.