I suspect the 333 actually fills a useful niche for AC on routes (mostly transatlantic) where they can't fill a 773 and 763 doesn't offer enough lift or enough J. IIRC the 333 is a relatively cost-effective aircraft.

The 330 has the same seating capacity as the 772 but would have lower operating costs, so unless they needed the range or lift for cargo, presumably they'd rather fly the 330 than 772.