These are really important for safety.
These simple little door safety retainers can save lives, and no doubt already have.
In 1993, ASME A17.1/B44 required safety retainers on both the top and bottom of door panels, in addition to door guiding means, to confirm the door panels would be retained should the door guiding means fail.
Door gibs can, and do, fail. Instances where someone inadvertently slams into the outside of an elevator door, or sometimes even just leans against one, can cause the door to buckle, and this of course can be disastrous if the elevator is not at that landing. That’s why safety retainers are required by code to prevent something like this from happening.