In the transcript of the Apollo 11 EVA on the Moon, Buzz Aldrin mentions closing the LM's hatch and being careful not to lock the two astronauts out.
109:41:28 Aldrin: Okay. Now I want to back up and partially close the hatch. (Long Pause) Making sure not to lock it on my way out.
(see https://www.hq.nasa.gov/alsj/a11/a11.step.html)
Why bother closing it at all, why not just leave it open?
Bonus question: Could they have actually locked themselves out?