The problem is there is no poll question 
So I interpreted it as “how often do YOU log out?”
I agree. I would say it gives me no benefit at all when I don’t need it.
Some sites I always log out, even on my own computer, for security reasons. Some sites I log out often because I need to switch between accounts. Some sites I never log out.
But IMHO there is not one good reason to hide the logout button. It’s like disabling the browser back button because you don’t want people to leave your site.