If they hadn't switched people would be complaining that they use such an outdated system as jake.
If pragmatism was their main concern, then they would have been using make, shell scripts and the common UNIX commands from the very beginning. This would have given them support for Linux, Solaris, the *BSDs, Mac OS X and a number of other systems right away. Windows could've been supported with ease by using the various ports of those tools. Those tools are extremely capable and well-proven for creating reliable, cross-platform build scripts.
I'm not sure why people are recommending make. Apart from the fact that it makes perfect sense for a library written in JS to use a JS toolchain, tools like Rake and npm are far more portable than any of the Autotools toolchain ever was. OSX uses BSD make by default for god's sake, and installing autotools on windows is not nearly as easy as installing node and npm. After that, you've got hundreds (thousands?) of CommonJS libraries that you can leverage where you control the version, versus having files sprinkled with comments like "// curl version <7 didn't support the -p flag, needed for WinXP cygwin v.24" (not actual example, but I've worked on many C/C++ projects where this is the case).
There are benefits when the entire community standardizes on something. I know I will frequently pass looking at a Python module that won't easily fit into my build system, which, conveniently, is the build system mostPython scripts use.
The fact that Cappuccino pre-dated the de facto standard should not be held against them.