There’s actually a really wholesome reason for it.

Have you ever wondered what inspired Panic! At The Disco to dress so dapper during their ‘A Fever You Can’t Sweat Out’ era? We have the answer!
It may be easy to assume that the reason for it is because Brendon Urie and Ryan Ross just had a flair for the dramatic – but it’s actually more of a functional decision.
In a recent chat with Ask Anything, Brendon was asked about the first venue Panic! played and shared “The first one we ever played at was this one called The Alley – that was right after we came up with the band name Panic! At The Disco. Before that, we were under a different name and I wasn’t even the singer at that point, and I’d just joined the band a month before… It was at my parents’ church. We played a church dance for youth. It’s pretty great.”
He continued “And that’s why the dressing up came into play – because there was a dress code! And I told my bandmates ‘if you wanna play this gig, you’re going to have to wear shirts and ties and slacks. You can wear sneakers, but you gotta wear shirts and ties’, so that’s kind of what happened.”
So the reason for it, was to meet the church dress code. Wholesome.
And after that, the aesthetic very much stuck – and we were all treated to an entire era of dapper, vaudevillian fashion.