He probably should have expected that someone else would turn up. Tony was hard on himself, but he cultivated a pretty extensive group of family and friends - far more than Sam did, even though to start with they'd probably been about equal in terms of their ability to meet people. It was the maintenance part where he fell flat. Either he pulled away or they did.
Bucky wasn't so bad though. He knew some version of Sam, but he got the impression it wasn't strictly a traditional friendship, and back home's Bucky had been little more than anecotes in a history book so that Sam himself wasn't able to waste effort on comparisons. And, well, you build someone a robot arm and you were bound to get at least a little bit attached. So he just shrugged at the question, not bothering to object to the interruption. "You know," he said; the same as most people, probably.