Mac cooks over a wood stove, and he seems to serve beer from his own bottles (though he may have a keg that I can't recall or that's not mentioned). I can't even remember him using a cash register or having electric lighting. I don't think he has much if anything that's going to be disrupted by spells, which I think is why nothing ever breaks down from hexing.
Actually I believe Mac has a number of ceiling fans, which do break down from time to time. Not as often as they would in the home of a wizard-level practioner, but more often than normal.
Also with regards to the whole number 13 thing, it a randomly arranged set of 13 pillars, as well as 13 differently sized tables scattered about the room, 13 stools at the bar, and 13 windows. In addition to the repeated used of the number 13, the whole point is for there to be randomness, or an absence of order to scatter and difuse any power that a practioner might be emitting accidentally. Put another way, it is really just about feng shui, as opposed to something which actively suppresses magic like a Threshold or Circle.
-Cheers