The upright and locked position of the seats is the preferred position in case of a crash or hard landing. I believe more accidents happen when either taking off or landing in an aircraft?

In the event of a crash/hard landing, passengers are going to be thrown around. If seats are reclined or tray-tables out, then they are a collision hazard for passengers. By preparing in advance, it saves people having to scramble to get into the correct positions in the event of a hard landing/crash. I think it is a psychological thing too - to tend to wake up and be more alert once the captain calls for seats up and tables away. Probably not a bad thing if it all goes pear-shaped.

The anwser is not so much that they are a collision hazard, (in a "crash"/emergency landing anything in the cabin could become a hazard if passengers are thrown about) but if not stowed they could hinder an evacuation if one were to become necessary. The reason F/As ask you to move the seat to the upright position is that it widens the space in front of the seats behind and locking your tray table up keeps your row clear of obstructions to egress. This is the same reason why all carry on bags "must fit completely underneath the seat in front of you", as any bags sticking out too far could create a tripping hazard in the event an emergency egress is needed. It is true that most accidents happen on takeoff and landing. Aviation safety studies have shown that approximately 90% of all aviation accidents occur during the first two minutes or the last four minutes of flight. Hence, those are the two times when a sudden emergency egress could become necessary. That is why the FAA mandates these things for the safety of flight and F/As must insure compliance for both of those phases of flight: Code of Federal Regulations; Title 14: Aeronautics and Space PART 121—OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS Subpart T—Flight Operations § 121.577 Stowage of food, beverage, and passenger service equipment during airplane movement on the surface, takeoff, and landing. (a) No certificate holder may move an airplane on the surface, take off, or land when any food, beverage, or tableware furnished by the certificate holder is located at any passenger seat. (b) No certificate holder may move an airplane on the surface, take off, or land unless each food and beverage tray and seat back tray table is secured in its stowed position. (c) No certificate holder may permit an airplane to move on the surface, take off, or land unless each passenger serving cart is secured in its stowed position. (d) No certificate holder may permit an airplane to move on the surface, take off, or land unless each movie screen that extends into an aisle is stowed. (e) Each passenger shall comply with instructions given by a crewmember with regard to compliance with this section.