They're rarer in Canada because it's cheaper for dealers to bring in piles of Chinese or Russian models, and they're more expensive to import. The US gets most of them because with the exception of the occasional Albanian or Romanian model, the Yugoslavian rifles are the only SKS's they're allowed to import. Chinese and Russian models haven't been allowed into the United States for a long time.
Another reason would be because M59's are less common in general. Most of them were converted into M59/66's in Yugoslavia, and many that weren't were beaten to death in the various internal conflicts going on in that part of the world in the 1990's.
They are also quite well made, but so are Russian and Chinese ones. If you're looking purely for a shooter, I wouldn't say it's really worth the price - A Russian or Chinese specimen will do everything a Yugo M59 will for a lower price tag, but if you'd like to own one for the history, novelty, or because you want one of every model, it won't disappoint. I hope to get one someday so my M59/66 has someone to talk to in the safe - she doesn't speak Chinese or Russian.