While at the Euro Speleo Congress at the Vercors in 2008, we saw quite a few different tackle bags at the equipment sellers' area. We found that not a single tackle bag had any drain holes, including ones often seen for sale in the UK. It appears that only Brit cavers want drain holes and importers or resellers add them for the UK buyers. It was easy enough to insert brass eyelets into the bags we bought when we were home again.
I too always have drain holes in my wellies, mainly to lessen the vacuum when trying to get them off, but with the added benefit that they also allow water to drain out.