The reason is partially to aid scripting, and partially security.
I have had people up to no good on my server, and my detection showed they were using action menu for their little tricks.
Would be nice to detect how many actions the player currently has. For instance if the scenario adds 12 actions via addAction, but they have 22 actions, that indicates something is wrong.
At the moment I have no way to count how many actions a client actually has in their action menu.
Assuming below QS_currentActions is a scripted array, adding each action to it for management. I can count the actions I add to the client, but not the total number of actions the client actually has.
if ((count (allActions player)) > (count QS_currentActions)) then { /* somethings wrong */ removeAllActions player; {player addAction _x;} count QS_currentActions;};