Certainly there are some inconsiderate customers who open boxes just out of curiosity, or open one package and then buy an unopened one.
However, Canadian Tire has created their own monsters regarding returns, and then get upset at customers who are trying to protect themselves.
In years past, if I had any doubt that an item wouldn't work when I got it home, I'd say to myself, "Well, if there's a problem, I'll just bring it back".
Those days are long gone, now that CTC has the "Repair Only" policy on some items, often refuses to take returns on defective items, and randomly refuses to take back other items without any reason at all.
These days, customers are being asked to assume 100% of the risk that an item CT has stocked on its own shelf is defective. Once the customer has paid for an item, it's likely that they will be stuck with it for life, or have to deal directy with the manufacturer - the new "You bought it, you're stuck with it, too bad if it's defective" approach.
So, it's only reasonable for customers to thoroughly inspect items, knowing that they may well be screwed out of their money if the item CT had on its shelf is defective, as so many of them seem to be.
That being said, I think that opening a package should be a last resort, and only with the intent to purchase the item that's in the box. Ideally, this is done with the permission of and in the presense of a clerk. Several times I've asked, "Can I open this? If it's OK, I'll buy it".
CT has also shot themselves in the foot regarding returns of defective items. Customers find themselves right back at the service desk with a freshly-opened box of some item or other, being told that if it's defective they are stuck with it. Gee, if only it was still good, and the customer had just changed their minds.
It should be no surprise that some customers, having innocently fallen into this trap, will yield to the tempation to say, "It's fine", rather than lose their money on a defective item that CT won't take responsibility for.
Then, the same stores that chose these practices turn around and say, "What bad customers! They open boxes in the store! They lied to us and said the product wasn't defective!"
How about allowing customers to return defective items that you stocked on your own shelves? How about dealing directly with the manufacturers who sent you defective items?
Oh, wait. That would cost you too much.
Yeah, your new system is much better.