Well, maybe because the fare difference between T and T+ on some intra-Canadian routes is quite significant.

E.g. I flew YYJ-YVR/YYC-YEG a couple of times this year and the fare difference between T and T+ was $140, nearly all flights operated by Jazz.

I would be willing to pay $30-$50 for the additional status miles and reward miles IŽd earn, and maybe a few $ for advanced seat selection, but apart from that I find it very hard to justify coughing up a hefty premium on the short-haul flights without getting much extra value in return, so I just book T fares.

Unless IŽd be a few k miles short of requalifying, IŽd probably never book T+ fares on these routes if I didnŽt need the flexibility (which I usually donŽt).