The answer is:

Wheel QRs go on the Non-Drive side by default due to the rear wheel. The lever or handle of the QR has no where to be closed properly on a multi gear bike with a deraillier. Or if the bike where to lose or snap a chain, it couldn't get wrapped around the lever and possible open it in a freak accident. The front wheel could go on either side, but to simplifiy things they keep it the same as the rear.

The quick release seat post clamps are on the right side because the majority of people are right handed and will thus operate them with their left hand. Almost all of them are reversable and can be flipped over the go the left if you chose to do so, but most people will stand straddling the rear wheel hold the seat with their left hand and open and close the lever with thier right.