I get it from a business perspective, you need to buy new stuff to keep the money moving. My Chromebook hasn’t and I suspect other mid-priced ChromeOS laptops won’t either. But those phones do break down, the batteries deplete and they slow down considerably by the end of those three years.
Six years is a long time for software support and that should be recognised, especially when most Android phones - including Google’s Pixel - offer three or less.
It is odd, then, that there is a pre-planned date for the Chromebook Pixel’s ultimate demise. But it still boots up instantly, runs quickly, has a nice screen and, most importantly, works perfectly well. Yes, the camera is a bit outdated (although laptop cameras are poor across the board regardless of price), there are better keyboards out there and it isn’t the lightest piece of kit. Chromebooks will continue to improve, new features will land and with them sturdier arguments for ChromeOS over Windows or macOS. They don't degrade under the weight of increasingly taxing updates that often breaks other, fuller, laptops. The point is that contrary to most other tech, Chromebooks get better.