Overhead bins are weight-limited to a certified figure.
(I seem to recall a labelled max weight of 70kg on B737. Can anyone confirm this?)
Let's say you have 3 (or even) 4 items in a 744 (drop-down) overhead bin. That's perhaps 100k.
Question 1
Who's going to close the bin?
Question 2
Who's brave enough to sit under it?
Not me, for sure...