Because that’s what heroes do refers to a memorable quote uttered by Thor in Thor: Ragnarok.
It became a popular reaction image macro online, used for commenting upon the gallant deeds of people, however, the phrase can also be encountered independently.
The meme originates from the third installment of the Marvel Thor movies, Thor: Ragnarok which premiered in the United States on November 3rd, 2017.
At one point in the movie, Thor (portrayed by Chris Hemsworth) is faced with the question why he doesn’t give up, to which he replies “because that’s what heroes do”.
The exact origin of the image macro use of the scene is not known, although they started emerging online in April, 2019.
A clip of the scene was uploaded to YouTube by MoviQuotes on May 10th, 2019 with the title “Thor Ragnarok – Because that’s what heroes do”.
The format would appear on sites like Reddit, Imgur, Instagram as well as Twitter and 9GAG.