Why does Saskatchewan always seem to take the brunt of the Canadian Jokes?

Bubba and Cooter - a couple of Saskatchewan businessmen wannabees were walking along the street in Medicine Hat, Alberta and they saw a sign on a store which read, "Suits $5 each, shirts $2 each, slacks 2.50 per pair."
Bubba said to his pal, "Cooter, Look here! We could buy a whole gob of these, take 'em back to Moose Jaw, sell 'em to our friends, and make a fortune.
Now when we go in there you be quiet, okay? Just let me do the talkin' 'cause if they hear your accent, they might think we're ignorant, and not wanna sell that stuff to us. Now, I'll talk like a person from Alberta so's they don't know."
They went in and Bubba said with his best fake accent, "I'll take 50 of them suits at $5 each, 100 of them there shirts at $2 each,and 50 pairs of them there trousers at $2.50 each. I'll back up my pickup and .
" The owner of the shop interrupted, "You folks are from Saskatchewan, aren't you?"
"Well...yeah," said a surprised Bubba.... "How'd you know that?"
The owner said, "Because this is a dry-cleaners."