Sherrinford nudged his head against Tony's hand, beeping and whirring affectionately as his creator stroked it gently. His metal tail wagged slightly and he clicked happily. Tony smiled contentedly as he worked one-handedly on a new circuit board design in his labs.
Contrary to popular belief (read: everyone in SHIELD and beyond), Tony didn't actually build robots in order to be his friends. To do that would be pointless and unrewarding, to say the least. Programming something to like him wouldn't help at all - he might as well pay someone to be friends with him and be done with it, for all the good it would do. It would just be tacky and fake.
No, Tony built his bots because he liked building bots. Whether they liked him or not, he left up to them. Several of the robots he had built had hated him with a passion, refusing even to venture near him. That had hurt a little, but he'd done his best to find them all homes with people they did like. No Artificially Intelligent robot of his would ever be given to someone who would treat them badly. Ever.
Tony simply built bots, and some of them liked him. Robots tended to do that - it was like they knew that he liked them, that he understood them, that he wouldn't hurt them. Because he would never hurt one of his creations, even if his life depended on it.
Admittedly, Tony preferred mechanics to humans, but then, who wouldn't? If they liked you then they would keep on liking you, no matter what happened. They wouldn't give up on you, woldn't write you off as a lost cause. JARVIS and Dummy had kept on waiting for him for months when he'd been kidnapped in Afghanistan, even though the rest of the world believed that he was dead. That was more than many humans would ever do for him.
Robots didn't turn on you (except in movies, and they were stupid), if they decided that you weren't the person they wanted you to be any more. Mechanics didn't lie, they stayed by your side. They didn't betray you after letting you think for years that they loved you and cared for you and believed in you like Obadiah had done. They sure as hell didn't betray you and try to rip your heart out of your chest (or near enough) and use it for their own profit. Robots stood by you throught thick and thin.
Perhaps even more importantly, robots could be fixed if they broke. If they were damaged or destroyed then they could be rebuilt, they could be saved. It just didn't work like that with people. Time and time again he'd watched people who he loved die and done nothing, out of sheer helplessness. You couldn't rebuild a person. He'd found that out again and again. Howard, Maria, Jarvis, Yinsen...
So Tony stayed in his workshop and built people who wouldn't leave him like the others did, every time, metal people who would last, who would survive, and who wouldn't break his heart. It was all he could do, really. He didn't let himself get attatched to flesh and blood people, who broke so easily and could never be fixed. Because whoever he made friends with nearly always ended up getting hurt. So he just... didn't.
Sherrinford purred, wrapping himself loosely around Tony's arm. The engineer-inventor-genius-billionaire-playboy - (except not that much, any more) -philanthropist smiled and stroked him happily. It might not be the most healthy thing to do, sure, but he was happy. He was safe, and he knew that his friends were, too. And really, that was all that mattered in the end.