....they were covering 60+ years of Art. It took them awhile to get through the absolute giants of the film, music, dance worlds. Then they added TV and then opened up the music award to newer forms like rock and blues and C&W.
There were probably 100 or more who deserved the honour but didn't live long enough to be honoured. None of the silent stars lived long enough. The Lunts were dead. The Barrymores and Kit Cornell were gone. Not to mention giants of the screen like Clark Gable, Humphrey Bogart and John Wayne, who died before the Honors even started.
When it comes to actors you have one or at most two a year. And that's film, TV and theatre. So there are always going to be omissions.