Do you mean when I am home or away? I ALWAYS lock when I am away. I probably do most of the time when home, especially after dark. I do often leave the door open so the cat can look out, but there is a secondary glass door that does lock.
Funny story - one time I stepped outside and found a hornet zipping around me. I ran inside and closed the door then locked it. My friend was there and asked me, "Did you just
lock the door so the hornet wouldn't get in?"

Yes, I did - you just never know, right?