Honest question about cosmic-greeter

It is really more than I need. So I installed ly. All good. But when I uninstall cosmic-greeter, because I want to keep as lean of a system as possible so why have things installed that I am not using right? Anyway, I cannot uninstall it because cosmic-session depends on it. So my real question is, why make your DE dependent on a DM existing? I am perplexed.