He very often either decides that he won't need something or simply forgets.
Sometimes we go out for the day and it emerges he has forgotten to the ake cash or plastic.
Once we were going for a long walk and before we left I put the OS map down beside him on the table as he was getting ready to go. Saying 'Here's the map' He didn't think to bring it.
At one point - some years back - there was a problem when he was out in the car. Thinking we were with the AA he rang them, and they said no were weren't members. So he had to ring me to get the RAC's number.
Just had a call to say he's broken down on a roundabout without any cards. So could I tell him the RAC number? No doubt a kinder person would feel sorry for him. I gave him the number and rang off without making further enquiries.