Are mostly unhappily taken care of by the Thinkpads. The brand has gone downhill since IBM sold to Lenovo, which has steadily eroded the level of quality that can be expected from a Thinkpad-branded laptop. Modern Thinkpads aren't nearly as serviceable or as durable as the Thinkpads of IBM's era.
People who stick with Thinkpads today tend to do so because a) the enterprise support is still relatively solid, b) no real competitors for the Trackpoint, if you want one you need to get a Thinkpad, c) the keyboard, while not as high quality as it used to be, is still great relative to most of the market, d) Thinkpads are still basically reference laptops for Linux, and as a customer, it's reasonable to assume that there will be good hardware support.
If System76 wanted to go after Thinkpads, they probably could.