1. git, until very recently (but haven't checked), requires you to check out the whole repo even if you're just interested in only a subdir or single file

2. Suppose you're implementing a Wiki where docs are version-controlled on a fs mounted by the web server. git doesn't really fit this use case since you'd need a shared checkout dir, whereas eg. RCS does, provided locking is accepted or even preferred

3. on-site version control of config files in /etc when you don't do full-blown DevOps

Because they want a DVCS that has less characters in its name, to save on typing? Mercurial [0] is a fairly popular choice these days, I believe, and uses 'hg' as its command line tool.

0. https://www.mercurial-scm.org/