12 is such a useful number given it has 2,3,4 and 6 as factors- lots of fairly simple mental math can get you pretty far.
20 is nice, but you could make the same argument for 30 (5x6). In both cases, there's too much overhead because you still have the useful 10 as a factor in any situation that doesn't need groups of rectangles.
I don't know if this adds much to the discussion, other than perhaps there isn't really a need for ranchers and bakers to use the same factors or base counting system?
Each of the four fingers on a hand has three phalanges, and thus three joints (not counting the thumb). That makes it easy to count to 12 on one hand, using the thumb to track which you're on. (I vaguely recall from school that this coms from Mesopotamia, but don't have a reference.)
One could make the same argument for 30, but 20 shows up repeatedly ("four score and seven", «quatrevingt-treize», 'Jiggit') and I can't think of any 30's. Months?
We've got 5 sausages to a jar over here, would go great with your 11 hot dog buns!
I've always wondered why sell that as a prime number, surely it can't be worth it to annoy your customers to sell them an extra sausage? Anyone introducing a reasonable amount would capture more purchases.
Or bags of bread with an uneven number of slices. Why are we inflicting this on each other?
Bakers count stationary things, so they like obvious groups of rectangles, and 3x4 is much nicer than 5x2, winding up with groupings of 12s.
To this day hot dogs and buns are sold in incommensurate packages.
(also, might 20s in numbering systems come about because 2x10 and 4x5 is a nice number for both ranchers and bakers?)