"This Is Why" was released on September 28, 2022.[1][2] It was the last song written for the album, at which point Williams was "tired of writing lyrics", although guitarist Taylor York convinced Williams and drummer Zac Farro to work on one "last idea". Williams stated that it "summarizes the plethora of ridiculous emotions, the rollercoaster of being alive in 2022, having survived even just the last three or four years" and thought that following the COVID-19 pandemic and "the impending doom of a dying planet", "that humans would have found it deep within themselves to be kinder or more empathetic or something".[2]
Quinn Moreland of Pitchfork wrote that the track "builds on the funky pop that colored 2017's After Laughter, but shifts away from its predecessor's bright gloss for something muddier and vaguely threatening" and called the chorus "spiky" with instrumentation from marimbas making for a "suspense[ful]" bridge, after which "the song creeps forward, ultimately never pulling itself out of its paranoid spiral".[9] Ali Shutler of NME described it as a "snarling, defiant middle finger to the haters" and a "giddy statement of purpose" with "newfound urgency to the party-starting music that takes influence from their angsty days as scrappy pop-punkers" accompanied by a "disco stomp".[8] Steffanee Wang of Nylon called it a "disillusioned anthem" as well as "explosive" and remarked that it "sonically fits in the neat in-between space between [the band's] older pop-punk stuff and the electronic contemporary sound of 2017's After Laughter".[10]
The music video was released the same day as the song, and was directed by Brendan Yates of the American punk band Turnstile and filmed in Malibu, California.[2] It depicts the band performing and "frolick[ing ...] in the Malibu wilderness, amid the grasses, against the blue sky, and [...] in the spare interiors of a house".[10]