It's not meant as a justification, but it may be out of ease. Both types look exactly the same, the only thing differentiating them is the silver content. You can't see this with the naked eye.
In the history of Numista several collectors have dropped their question on the forum how to distinguish coins from the Canadian 1967 Confederation series, which exist in .800 and .500 purity. Quite recently, user Rsirian1 demonstrated that it seems to be possible to distinguish between the two using a neodymium slide:
https://en.numista.com/forum/topic128773.html#p1042674