I do not use debootstrap for educational purposes but to bypass
installer misbehaviour.For instance, I remember using it when the
installer obstinately wanted to force me to use LVM (Logical Volume
Management). This happened both under Debian and Devuan. On other
occasions, the installer came to a mysterious halt because it wanted
to use a network connection even though I had a CD in the CD drive
from which the installation was running! Installers remind me of
myself losing hours upon hours attempting to make them see reason and
install to a partition or use an already existing partition without
formatting it. Well, I cannot allow it to format my home partition.

In short, I found debootstrap very useful. Unless installers are made
to do what the operator wants them to do, they become time-wasters.