Aptitude normally follows the Suggests & Recommended dependency levels, so it can end up installing packages that aren't actually required for another package to function but simply go well together.

This behavior can be permanently configured from the aptitude menu (F10) The change is saved at ~/.aptitude/config:

$ cat ~/.aptitude/config
aptitude "";
aptitude::Keep-Unused-Pattern "";
aptitude::Delete-Unused-Pattern "";
aptitude::Recommends-Important "false";

The corresponding configuration option is Aptitude::Recommends-Important which can be overridden by

-R, --without-recommends
       Do not treat recommendations as dependencies when installing new
       packages.

-r, --with-recommends
       Treat  recommendations as dependencies when installing new pack-
       ages.