Can be disabled while logging out (untick the checkbox) or holding shift while logging in.
There are still important state details that aren't preserved, like how far down the page I've scrolled in an article I'm reading, a form in progress, or the text that I have highlighted in a tab. How about my active terminal sessions in iTerm? It would be a joy if that state preserved across restarts.
For example, in tab #1, I cd and run a bash script to start a web server process. In tab #2, I split it into two panes, and in #1 run workon to start a virtual environment then start the Python REPL. In pane #2, I run top.
After quitting and restarting, tab #1 returns to the proper directory but with no output. Pane #1 shows previous output and returns the proper directory but without the virtual environment activated. Pane #2 does the same. History seems to be merged across the three which is a bit confusing as well.