Apostrophe's 'Should Not Be U'sed In Front Of Every 'S

Ack. All I can see is the awful randomly placed apostrophe; "words", plural, should not have one.

See The Oatmeal's excellent summary of the rules of usage.

Y'all

Why is it that the same people who invented the word "y'all", being short for "you all", insist on spelling it "ya'll", being short for...?