I don’t do it. Did it when I was a newbie. Quit doing it and never will again.
Back before electronic access to lockboxes, about the only way for a listing agent to know a house got shown was for the buyer’s agent to leave a business card inside the house somewhere, usually the foyer or kitchen counter. It is one of those practices that should have died long ago but hasn’t.
I don’t like it when agents leave their cards in my listings either. See, nothing tells a buyer and their agent that a house isn’t selling like seeing a big stack of cards from showings that did not result in a sale. Heck, sometimes I have seen so many business cards that it looks like some kind of drawing for a free gym membership by the register of a Pizza Hut. As an agent, it makes me assume the house is overpriced or has some fatal flaw that nobody wants to own.
Besides the fact that I am the only Realtor that doesn’t carry 500 business cards with me everywhere I go, the main reason I never leave one is so no other buyer’s agent knows I was there. See, I have been in multiple offer situations before and known who I was competing with because I made note of whose card/cards I saw while at the house. I hit their recent sales activity on the MLS and look for patterns like what percentage of the list price do they normally get their clients to agree to, do most of their clients ask for seller concessions, what type of financing most of their clients do, etc. Often, I know a little about the agent anyway since I have been around for a while.
BTW, I ordered a box of 1000 cards about 4 years ago and I think I still have about 983 left. I’ll dust one off if you want one?