Because it rhymes with day.
Also, the company was happy, we partied all night is essentially what that line is saying. They were happy because they stayed up all night having fun.
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The Party told you to reject the evidence of your eyes and ears. It was their final, most essential command.
If you're not careful, the newspapers will have you hating the people who are being oppressed, and loving the people who are doing the oppressing. —Malcolm X
Just a reminder: under international law, an occupying power has no right of self-defense, and those who are occupied have the right and duty to liberate themselves by any means possible.