I don't think anyone nowadays is buying a mechanical watch primarily for its technical performance specs. I think it is primarily for aesthetics and history, also happens to be very practical jewelry.
Now that said, when someone has decided they want a mechanical watch because of the reasons above, then specs do come in to play. It is pretty cool that a machine powered by gears and springs can tell time pretty accurately, and more accuracy is better although accuracy is not the only (or even primary) criteria. Same with other specs like water resistance, antimagnetism etc. None of those are reasons to buy a mechanical watch, but once someone has decided to buy a mechanical watch, those do come in to play. Still for me the looks and history are the most important factors.