These United States have an irrational fear of dying. Americans don't want anything to end, neither tidily nor suddenly. The going consensus is to let shit just go on as long as it can.
This is why euthanasia is such a hot button issue. Even if someone's life is utterly hellish, we can't let them die! That would be a sin against humanity to let that terminal cancer patient take his or her own life, god dammit!
This is also evidenced by the Police Academy movies.
Look at Japanese anime. Sure, some of it drags on and never ends, like Pokemon and Dragon Ball Z, but there's a lot more mini series' that end gracefully and rocked ass. Photon. Trigun. Evangeleon.
You would never see these sorts of miniseries in the US. Production companies would squeeze them until they could no longer reap a profit from them.