Tarot, by its' very nature, is subjective. Just as there is no definitive list of what the cards means in every situation or to each individual, there is also no list that says "you must do this" or "never do that" when it comes to reading cards.
If one feels cards are purified by salt, by all means, salt 'em up. There is no harm done to anyone. There is equally no harm in not salting the cards, if you do not see the benefit. Some people find rituals important and comforting, and some do not care for them. It's personal, and we should honor what resonates within our hearts.
There are two little dishes of salt on my altar, one black and one white, because I do think it has a place there, for me. But there is no salt near my cards, unless I happen to be using them on the altar, and I have not had any adverse effects.
Ultimately, I believe that tarot is a tool, an amazing and wonderful tool that should be used respectfully and valued, but like all tools, it makes a job easier, not possible. I believe tarot cards are like Dumbo's feather. He could fly all along, but grasping it made him believe in magic.