JARVIS being Iron Man‘s closet ally, at least at the start of the MCU, explains his biggest problem. When he was first introduced in 2008, Tony Stark was a self-absorbed industrialist who couldn’t be bothered to think about other people’s needs. Throughout his journey in the Infinity Saga, he evolved into a much better person. When he ended his arc in Avengers: Endgame, it was a 180-degree transformation from the man he had been in the first Iron Man movie.
Long before he created the first suit out of necessity to escape his kidnapping in Afghanistan, Tony was already an established genius. Like his father, he had a knack for building things; he was behind most of the creation of Stark Industries and was the main reason why the MCU’s Ten Rings wanted him in the first place. Outside of his weapons, Tony also created robots with Dum-E and U, which mainly helped him in his personal workshop. But arguably his most impressive creation prior to the Iron Man suit was Just A Rather Very Intelligent System aka. J.A.R.V.I.S. — his natural-language user interface computer system that acts more like his personal assistant.
Named after his father’s own butler, Edwin Jarvis, J.A.R.V.I.S. was at Tony’s beck-and-call. Not only did he assist the Avenger in refining his Iron Man suit, as well as providing support during battles, but he was also a constant presence in his house. Despite being an AI, J.A.R.V.I.S. interacted with Tony almost as if he were a real person, only without a physical body. While this was significantly helpful for the genius, billionaire, playboy philanthropist in his research, it also kept him in his solitary bubble for far too long. Since he had J.A.R.V.I.S. and a few other trusted allies in Pepper Potts, Happy Hogan, and James Rhodes, Tony was more than happy to keep his circle small. This made it so much more difficult for him to work with others once he had to open up to be able to do his job well as Iron Man. This was best showcased in The Avengers and the first half of Avengers: Age of Ultron where he pretty much did whatever he wanted to do without consulting the rest of the team.
In hindsight, Tony primarily interacting with J.A.R.V.I.S. since the AI’s inception highlights how tragic his story truly was. He had unlimited reimgs, not to mention a genius brain, but was sad and closed off for a large portion of his life, feeling isolated and lonely. He had issues with his parents, particularly with Howard Stark, so when they died, he still had those hang-ups from his unresolved problems with them. J.A.R.V.I.S. was his friend, so when he technically died in Age of Ultron, Tony must’ve been heartbroken; unfortunately, he wasn’t able to fully grieve as he had to deal with more pressing matters. When he was reborn as Vision, the relationship between the pair was never the same. In fact, the pair’s final interaction on the screen was way back in Captain America: Civil War, before both of their deaths in Avengers: Infinity War and Endgame, respectively.
As Marvel Studios continues Vision’s story in WandaVision, it’s curious if his history as J.A.R.V.I.S. will ever be explored. The Disney+ show promises that it will explore both of its titular characters’ arcs in the MCU leading to their present situation in Westview. For Vision, that should include his time as Iron Man‘s trusted AI support considering that it’s technically how he first started in the franchise.