Stunt people are basically no different from makeup artists, SFX crews, and sound technicians. They are talented people who put a lot of effort into creating a finished movie. However, when someone wins an award for, say, sound production, I doubt it would occur to them to thank the stars for having such easy voices to record.
Natalie Portman did the *acting*, and won an award for *acting*. Really, unless we want every winner to read off the credits to their films, they are entitled to figure the award concentrates on their work, not everyone's. If anyone were to thank Ms. Lane, I think it should be the director and producers, who oversee the entire production.