The Threepenny Opera has had it with its own characters. It's doing everything it can to show its audiences just how awful and hypocritical they are, exposing their lies and deceit at every turn. For example, this tongue-in-cheek statement by Brown, the royal official on horseback who comes to reprieve Mac, is chock full of sarcasm and derision:
BROWN. The castle of Marmarel, likewise a pension of ten thousand pounds, to be his in usufruct until his death. To any bridal couples present Her Majesty bids me to convey her gracious good wishes. (3.9.350-353)
The completely unexpected and unfair riches, which Mac, a murderer and thief, clearly doesn't deserve, are like a slap in the face. At the same time, the snide remark about the "bridal couples" reminds audiences of the phony marriages Mac has to both Polly and Lucy. The play just seems tired of the way things work and the injustice of humanity, and it is begging the audience to notice and do something about it.