I'd imagine it's because it's available everywhere (even openwrt routers and those things), and it's easier to get away with not having to use sudo (depending on the task you are doing, of course). With Ansible, you almost always need python installed on the target host. Which, in 95% of cases is not a problem. It's not ideal to install a system package just because you want to do some provisioning (there are ways around that, but it gets hacky pretty quick...).
I haven't looked at this yet, but I really like the idea. Always wanted to have something like this for a few special cases. And if it's well designed, it could be a nice, lightweight and portable solution to do server provisioning, development project setups, use in Docker builds, etc.