Most customers care about having the best of the available options. Rarely would any company deliberately choose to be behind where their competitors can be.

1. The way to run into undiscovered issues is to choose a completely custom firmware/hardware/software stack that almost no one else in the world is running.

2. Not sure where you're getting this from. There is almost always a price:performance calculation that results in current generation smashing the previous generation with server and switch hardware. Often this means not buying the flagship chips but still the current generation.

And a major reason to get off old generations of hardware is that they become unavailable relatively quickly. It's always easier to buy current generation hardware than previous generation hardware, especially a couple years into the current generation. This has nothing to do with chasing the latest hardware.