USA TODAY "Mom" is a critically acclaimed comedy with a hopeful message about recovery that's thriving creatively in its eighth season. So why is it ending now? "That's a wonderful question. It was not something we wanted," executive producer Chuck Lorre says in advance of the CBS sitcom's series finale Thursday (9 EDT/PDT). Lorre says he was surprised and disappointed when he learned in February that "Mom," which centers on a group of friends who support each other in recovery from addiction, would end this spring, a feeling shared by cast members on social media. He says he was told the series had become too expensive, given the rising costs – including salaries – of a long-running popular comedy, but that he doesn't know the specific reasons behind a decision that would have been discussed by CBS and Warner Bros. Television, the producing studio.