On recent full flights, I noticed that passengers after me tended to load overhead compartments in a suboptimal fashion that failed to maximize the amount of baggage that could fit in each one.

The usual situation is that a passenger with a rollaboard would not even try to put it in wheels-out or handle-out (so that the long dimension is perpendicular to the aisle). Instead, they just put the rollaboards in parallel to the aisle, wasting overhead space. Flight attendants did not even try to turn the rollaboards that direction when looking for more space for later arriving passengers.

Any reason why people (including flight attendants) seem to be unaware of optimal overhead compartment packing?