I actually started to work on a 10x10 grid but a decision from the PSP was to stay on the 10x12.5 grid, at least for now.
I did make sense. Remember the field was 125' wide a few years back, thus the 12.5' marks.
I think a lot of fields have either painted lines on their turf or a setup already in place with that grid. That could have been part of the decision.
It doesn't really matter... I don't know how you guys setup your bunkers but we simply pull tapes from the side lines, zero on snake side and place our bunkers that way... So if a bunker is a 72', 23' 3/4 or 40', it doesn't matter... just read the tape and place your prop.
You cannot solely use a grid to setup a layout. There always are offset bunkers... you need to pull tapes anyway... so the grid could be anything... Just my opinion though...