Game #1 ends - You have been discarding from the right during last game and placing your new cards on the left. Your teammates have noticed this and knew when to warn you not to discard certain critical cards.
Game #2 starts - You are about to discard your first card of the game. Which one would be safer to discard?
Actually, you are not here to be a traitor or something, this is a cooperative game, you don't want to trick your teammates. Therefore, the most sensible, most likely, most predictable slot your teammates will suppose you will discard from is the same slot you discarded from during the last game. So why not discard from there? Because the game allows no communication, therefore you should be as predictable as possible. Logic wins.
Yeah, mate, but you complain about leftism being conventional. That's pretty much the same, bro.
Actually, it's pretty different.
Discard order is about safety, while conventional leftism may be dangerous in some situations because it is about getting cards played. A wrong play results in a strike, which in turn may result in a loss. If you apply conventional leftism to starting hands, you miss out on a lot of good clueing opportunities.