Why are data files stored in /var/lib

Hello

I use version 9.5 on Linux Mint 17.3.

I had a discussion yesterday with some friends, who are sysadmins about the location of database files. In a default installation
from a distribution (apt-get install) PostgreSQL creates a cluster unter /var/lib/. According to my colleagues /var/lib should not
contain data that is supposed to last over time. I am aware that the location can be modified to suit the needs of sysadmins as
described under these links.

http://www.postgresql.org/docs/current/static/storage-file-layout.html
http://www.postgresql.org/docs/current/static/runtime-config-file-locations.html

In the first link there is a line stating that "A common location for PGDATA is /var/lib/pgsql/data". My question is if there is a
specific reason for choosing /var/lib as the default for database file locations, some kind of best practices or alike. I assume
that there have been discussions on the topic?

Thank you and enjoy the weekend.
Charles