What is apt-get equivalent of "aptitude why"?

Question

In this answer, I came across this command:

aptitude why firefox

aptitude whylooks like an useful command but I don't want to install aptitude just for that. What is the apt-get equivalent of aptitude why?

Answer 1

Instead of apt-get I would have a look at apt-cache, though not one on one the same but close will be:

apt-cache --installed rdepends firefox

Answer 2

People might want to know why an automatically installed package is present on the system. To get this information from the command line, you can use aptitude why package

apt-get has no similar feature

source:debian-handbook