yeah I have a feeling graphing calculators are primarily a US thing - UToronto only allows the Sharp calculator as well. it's pretty apparent when you compare the amazon links (and if we're using amazon reviews as a metric for popularity/usage):

Sharp 520 in Canada has 5 reviews compared to the 6 reviews of Sharp 520 in US aka barely any difference

on the other hand, TI-89 in US has 700+ reviews compared to the measly 4 reviews for TI-89 in Canada