The last repost, that's what drives me nuts when online smartarses say "durr why would you expect plot logic from eg. A show about a time travelling phone box/man who can fly/giant robots". THERE HAS TO BE INTERNAL LOGIC OR IT'S JUST LOTS OF STUPID SHIT HAPPENING
You underestimate the LOUD NOISES WOW contingent.
This is why the last two seasons of Doctor Who were a bust - viewers couldn't rely on the writing to pay out properly. A+B don't always have to equal C, but there has to be a good internal reason for the next letter - ta da - to be Z.