Why is the Mac OS X login screen slow?

Question

macOS

After the reboot, the login screen appears. He spawns at around 15-20 FPS per eye.
The latest retina macbook pro, the latest macbook air, and the latest macmini show the same picture. Just do not need to fanatically tell that everything flies with you. I looked everywhere I could - everywhere it is and there is no need to turn a blind eye to it.
I have a question - why? And can something be done about it?
And in general, such a lousy interface rendering speed (yes, at least 16GB of RAM, it's still lousy against the background of both Windows and Linux) - is this a problem exclusively for Mavericks (for the sake of battery life) or was it the same with a mountain lion?