Right, and a proper packaging "in the box" reduce it to a single install command on most any Linux. Right now it's pretty close to that on a Mac also if you already have brew.

The current long pole in the tent is Windows. Bazel brings along its own JVM - so there isn't any Java or Java dependency difficulty (as some other posters have suggested). But the install instructions direct you to provide some dependencies first, by hand. Of course in the long term a little while spent installing is no big deal... but each new adopter has to get through the short term on the way to the long term.

Hopefully a future Bazel installer will "just work" on Windows as a single installation with no instructions.