Most (all?) legislations require that people moving in from other legislations need to exchange their driving license if they wish to continue driving. Ontario is no exception.
Suppose somebody is told they need more practice, because they moved to a big city where traffic is more difficult to navigate than where they got their license and where they're used to driving. Suppose this person decides to drive with a license that would be perfectly valid elsewhere, just not exchanged. If the police pull over, how likely are they to find out? And if they do find out, is it "driving without a license" (apparently a 325$ fine and a "3 year conviction"), or is the consequence different?
This is all, of course, entirely hypothetical...?