You raise a good question as this goes beyond Canadian citizens. A US citizen could, for example, be denied entry to Canada if they had a criminal record including a DUI. Because this affects a person’s ability to work, if their work would involve visiting Canada, it is something that has to be cleared up, or remains an ongoing problem.
I ran a search using Legal.com’s Find a Lawyer search engine, and discovered that there are a number of law firms available to clients who wish to seek the ‘record suspension’ and ‘pardon’ status referred to in the link you posted. The search term I used was “canada pardon record suspension” – it took Google a half second to find 126,000 results.
I know of people who have successfully sealed their records to achieve pardon / record suspension status in Canada, allowing them to freely travel and work there. You raise a valid point and one that is worth looking into to eventually move past an event occurring years in the past.
Best, — Dave