It won't make flying more secure. E.g. if there are more people gaining access to the cockpit, that is more people who will have the opportunity to crash the plane if they decide to.

It's window dressing to address the concern that's in the public's mind concerning flight safety, and reduce the amount of money lost to airlines due to people deciding not to travel.

This is a common situation. When something newsworthy happens, measures are taken to address it as this is what the public is concerned about. The fact that other dangers may increase due to the measures taken doesn't matter, as the highest concern of the airlines is to address whatever the public is most worried by now. Which after this flight and MH370 is pilot suicide.