Until Wikipedia settled the issue (complete with footnotes!), it had been a topic that no one had a definitive answer to.
Why do we always play Queen classics We Will Rock You and We Are the Champions back to back?
There are obvious synergies between the songs. They are bookends to a story. They complete the question "Who rocks you? We do, therefore making us the champions." It's not super complicated- but is that enough of a reason to play the songs back to back?
Perhaps not- but then there's this tid bit- "We Will Rock You" was the B side on "We Are the Champions". So, from the moment they wrote the songs, the band planned to have them together.
But wait! They are not the right way around. "We will Rock You" was the B side, meaning you'd play "We are the Champions" first, not second as we do.
So that theory fell over.
In the US however, the single was regarded as a double A side and that's where the pairing of the two songs really took hold. Throw in the fact that the band always played said songs in the "correct" order and always together live and the theory progresses into fact.