> Are you wasting your money on branding when you could just install linux on any old computer and be fine.

Many developers just don't want to put up with the hassle of installing and maintaining a Linux environment. Just yesterday I've helped a friend installing Arch on a ThinkPad T440s and we almost gave up due to libinput bugs that made the trackpad pretty much unusable (fixed by a few hours of trial and error and then going back to evdev). We still have to get the Intel wifi to work decently. Apparently some glitch with power management doesn't let it achieve full throughput.

OS X (and even a clean Windows 10 install in most cases) pretty much work out of the box and let you focus on actual tasks.