Many Boeings have a minimal checklist attached to the control wheel. My company never used these but there was a sliding marker along one side presumably meant to be used as an aide memoir for how far through the list you had gone.
I made it a habit to use this as a cleared to TO/land indicator - up for TO, down for land.
It was comforting when the FO asked on short finals 'did he clear us to land?' to have something to confirm that 'yes, he has' rather than suddenly wondering whether that was actually on the last sector.
Those who minimise the seriousness of not receiving a clearance may not have had the experience of someone taking off on a runway which crosses the one on which you are just rolling out. I can tell you that it produces a distinct tightening of various sphincter muscles!