Why does Ubuntu take so long in first login?

I have been seeing this problem for a long long time in Ubuntu!

Whenever the system (re)boots, the first login (i.e. the time between entering the password and hitting Enter and the desktop appears) is about equal (or sometimes more) than the boot time (i.e., the time the entire booting process takes until the login screen appears).

I haven't seen this behaviour on any other OS!

Why is it so? Is there something inappropriately set in the system settings? How to see exactly which process takes how much time in the login process (just as we use systemd-analyze for monitoring startup processes and times)? Is there any workaround to reduce this login time?

Any assistance is greatly appreciated.