$ docker run --rm debian:jessie less -V
docker: Error response from daemon: Container command 'less' not found or does not exist..
$ docker run --rm debian:jessie more -V 1 ↵
more from util-linux 2.25.2
It's using debootstrap --variant=minbase, which (from the man page) "...only includes essential packages and apt." It makes sense that docker would want only the bare minimum. And to be fair, but getting into nit-picking territory, minbase is the default for debootstrap, but debootstrap is not the default method of installing Debian: debian-installer is. So docker's Debian image doesn't install less, but they're not doing a default install, as in invoking debian-installer, and keeping the preselected choices as much as possible.