“I don’t have anything to hide because I think I’ve done something wrong: I have something to hide because I question your judgement and motives.”
They’re fine giving you their info because they trust you. The problem is when the person seeking that information is untrustworthy – and some shithead(s) making their way into a company or government isn’t just possible, it’s likely.
Tell them to give all their sensitive personal information to someone that hates them. Credit card numbers, political beliefs, nudes, sexual preferences/fetishes, etc.
Various other things like leaves, rags, sponges, or leftover paper. Failing that a bare hand works: manners dictating you wash it after.
Some cultural hangups on the left hand being “unclean” stem from those cultures using that hand for hygienic reasons.