Avengers 4: 8 Major Plot Predictions
8. Hawkeye's Motivations
Hawkeye was notably absent from Infinity War, despite many of us just assuming he'd make an appearance of some sort. How wrong we were.
The movie explains his absence with a brief, easily missable line of dialogue which comes during the scene where Cap reunites with Rhodey at Avengers HQ. It's mentioned that Hawkeye and Ant-Man/Scott Lang - who were busted from prison at the end of Civil War - took a deal that would keep them on house arrest, a decision that was made because they both have families to consider.
We don't necessarily know that this is true - the Avengers don't exactly have time to keep tabs on him, and he could really be up to anything - but if we take this explanation at face value, then Hawkeye's motivations in Avengers 4 become much clearer.
Since Thanos wipes out half the universe at the end of Infinity War, there's a good chance that Clint's family were among those who disappeared in a cloud of dust. With no family left to protect, Hawkeye now has a reason to step up and help the remaining heroes rectify the situation: he wishes to save his wife and kids.