The thing that throws them off, dear deadhippo, is the existence of the 窶毒 unit.
Try writing a 12 digit number with the commas every 4 places instead of every three and then see how easy it is to read it in Japanese.
123,456,789,012
versus
1234,5678,9012
1234窶ーツュツ 窶售窶啅窶啖窶啗窶毒督 窶唸窶唹窶啀窶啣
See?