They want to keep the finale entertaining. May GoT fans have personal ties with either Jon, Daenerys, Sansa, Arya, Bran, Tyrion, the Hound, etc. If they were to kill one of them off before the final season, those people who had those personal ties with that now dead character may be less interested in the final season. It's entirely suited for the viewer.
Jaime IMO, killing him off would of been so wrong. He is bar none, in my opinion, the most interesting character in the series. Not to mention he has the greatest character development I have ever seen in a television show. I wanted him dead after the first season, now I pray he stays alive. He still has a role to play.