After some Code 6 Turbulence that I experienced last year where I found pieces of a "small" laptop strewn through the cabin with a few displaced PSU panels.... I agree with the rule. Not to mention putting items of mass in there only stretches out the seatback so that it sags.... and eventually those metal bars snap.

Rules exist for a reason. Maybe instead of the "what about ME" attitude we could realize that we don't need to have everything we own within 3 inches of our body for each flight and that some rules WILL inherently inconvenience you, that's just part of living.