Why ask for a threesome?

So yesterday after having a wonderful Nooner, my DH and I are laying there and he asks me, “So do you want to have a threesome”? I immediately think ‘omg why is he asking me this? I can’t handle two of him. Does he want someone else? “. I say, “NO” and a few minutes later I ask him if he wants one. He says “No. I read somewhere that if you ask your partner if they want a threesome and they say yes, it means you aren’t satisfying them sexually”. What are you thoughts on his comment? Why do people ask for threesomes? I think he got this from a meme.