I have to agree with both dpenabill and Lammawitch.
Once you are established in Canada, already have a job, have health care, have a drivers license, in my experience, nobody asked me for a PR card any more.
However, if you move to another province, you may be asked for it when exchanging your drivers license or when signing up for health care in your new province. Some employers even ask for them which means you would have to convince the employer that you don't need that or lose out on the job. I have heard of college students being asked to provide them as often as every semester to prove that they are entitled to pay the lower tuition fees for PR's and citizens instead of the higher fees for international students.
There is one more point I can think of and that when you are outside Canada looking to return and that is that even though you are visa exempt, if you can not show that you are a PR, the airline could require you to buy a return ticket. I remember having heard about that happening to someone on here.
The PR card hasn't actually been around that long in the terms of immigration and government. It is actually only 13 years old. In the beginning, it was only thought as a travel document for PR's, to make it easier to ID a PR when they return. However, in the meantime, all kind of agencies inside Canada have realized that the PR card might also be a good way to establish that a person has valid PR status. Of course the lack of a valid PR card does not necessarily mean you don't have PR status if you meet the RO. We know that, but the person who you are asking to issue you a drivers license for example and is supposed to verify that you have the right to live in Canada doesn't necessarily know that, nor do they want to go through your travel history with you to indeed make sure that you meet the RO. They just want to see the card. You can argue with them but arguing with bureaucracy is normally pointless. You can sue their agency if you want to but most of the agencies have more time and more money than you do so the path of least resistance is simply to go with the flow and renew your card.
As for the renewal being a hassle, maybe, but it's only every 5 years. As for it being a cash grab, a PR card is $50. That probably doesn't even cover the costs. I think $50 every 5 years should be affordable for everybody.