It's just something to do with their accent and the way they pronounce it. Not sure why they take U's out of some words and replace S's with Z's, though. Likely the same reason they still follow the imperial system, where the rest of the plant either uses Metric, or a combination of the two. ;)

I'm American and I don't understand it in the least either. Where I live, "cows" should be spelled "kowz". Hmmm..