Why don't the Other Avengers Get Involved in the Films?

One question I constantly see popping up is "Why the heck doesn't <insert Avengers character here> just ring up <insert other Avengers character here> and get them to help them out?" Well, since I love the Avengers movies (and secretly want to befriend Tony Stark to get a suit, but that's another matter), I'm going to try and explain for each movie why they didn't just get the others involved.

For the ones before the Avengers were set, it's quite simple. They just don't know each other yet. Especially for Captain America: the First Avenger, since most of the members aren't even born yet. That just leaves Iron Man 3, Thor: The Dark World and Captain America: The Winter Soldier (since seriously, how would they even get involved in Guardians of the Galaxy?). The rest of the time, the main reason is that it just happens too fast for them to get message out and get the Avengers Assembled in time.

Black Widow and (maybe) Hawkeye

This isn't a movie, but a reason why neither get involved in some of the movies (admittedly, Black Widow gets involved rather often). They're both Shield Agents outside of the Avengers, and as such have work to do, with isn't necessarily going to clean up the Avengers mess. Plus the army may specifically ask the two of them to stay out of certain situations, for reasons that could include wanting to save them for more important situations, wanting to send in the army or Iron Patriot instead, or simply (especially in Black Widow's sake), not exactly trusting them to put the government interests above their own (especially during the Winter Soldier, when Shield were against Captain America).

Iron Man 3

You might not have noticed, but Tony Stark has a huge frigging ego. Even he admits he doesn't play nicely with others. So why would this guy, who's being personally targeted, ask others for help? It just doesn't fit his characterisation to phone up and call for help. Even if it did, he's also suffering from an extreme case of PTSD from the Battle of New York, and so probably wouldn't want to get involved with anyone from that (since a symptom of PTSD is wanting to avoid events that remind you of the trauma, and so he could be avoiding going into battle with any of the Avengers because of that). This could also be a reason why Iron Man isn't present in any of the other movies: he's simply refusing so that he can get over the Battle of New York and get himself emotionally better so that it's possible for him to appear in Age of Ultron. Even then, he's not going to be able to contact the rest of the Avengers most of the time, since he's asking a huge favour of the kid in the first place, without bringing all the Avengers in to raid his house. Whilst it could be argued that the Shield ones could be brought in when Iron Patriot was, it's possible that they were just doing another job at the time or Hawkeye could be taking leave to spend with his pregnant wife.

Thor: The Dark World

The first part is set in other dimensions, and its considered extremely unusual for a human from Midgard to travel to any other dimension. None of the other Avengers have the ability to travel through dimensions, so they couldn't come to help him even if they wanted to. His friends wouldn't necessarily know the Avengers, and if they did, they probably wouldn't have any way to contact them and by the time Thor himself got back he was too busy to contact them. Plus the fact that he ends up battling Malekith through multiple dimension, and having seen what happened to Jane when she went through the portal, he probably wouldn't want the others entering the portal for the same to happen to them and for him having to deal with a bunch of unconscious bodies whilst dimension hopping. While this is excluded for Iron Man, Thor is a nice enough person to not ring his friend up and say "Hey, I know how the last time you travelled through a portal caused you PTSD, but I want you to come and travel through a bunch of portals and do exactly what happened last time, want to go for falafel after?"

Captain America: the Winter Soldier

He's wanted by Shield. That counts out Hawkeye (Black Widow is actually involved, and might even persuade him not to get involved for his family's sake). Plus it means that Shield are probably tracking him and the people he might contact, including the Avengers, or at least he might believe that they can, so he doesn't want to risk it. In addition, in the movie he finds out that Hydra's using satellite lasers to eliminate anyone that might go against them, so he probably wouldn't call them once he finds out due to being a nice enough guy to not make his friends the target of satellite lasers! Geez, I thought we trusted Captain America to be the nice guy. Nice guys don't attract death lasers to their friends, especially when they might not be able to find him fast enough to actually help without giving enough information that Shield can find him and arrest him for being a fugitive for reasons.

Now you may argue that the hero themselves don't need to call the Avengers up for them to be summoned, but most of the films have the heroes relying on secrecy and so there wouldn't be anyone who knew enough to phone the others, but not be busy enough to get all the Avengers set up.

So yeah. Reasons. Lots of reasons. By the way, Antman and Deadpool have the same reasons that the earlier Avengers movies do, that they probably don't have the Avengers phone numbers to call them up to help.

Now for a bunch of other movies to come out so I have to do this all over again!