For those of us who's traditions trace back to Europe...
Horses are (were?) mounted from the left, because all good Knights fought right handed, therefore your sword hung off your left hip. So it's much easier to mount with that leg staying on the ground and swing your right leg over the hind end of the fine steed.

We're culturally geared to mount and dismount from the left.

I'm not so certain about Asian cultures and horse mounted fighters.


My brain won't let me mount my bike from the right, unless I can step-through. Walk around to the left side, swing my right leg over the back wheel. The only way.