I think I first saw a Star Wars movie when I was about 4 or 5. It was Return of the Jedi (recorded off the telly) and I got to just after Luke showed up before I lost interest and went outside to ride on my peddle tractor. I remember asking later if they rescued the green girl from being eaten by the slug man. In the original cut Oola just disappears and the shot immediately cuts to Jabba eating the frog, so my young brain assumed that the frog was Oola and that Jabba ate her.
So yeah, "appropriate for all ages" doesn't mean all ages will want to watch it. There nothing inappropriate about about an educational video about the history of cricket...but good luck expecting a 4 year old to sit still for it...or for a 2 year old to even be aware it's on.
Side note: I wasn't much older when I first saw 'Aliens'. Or rather, the old man had it on and I was thoroughly bored before Sigourney Weaver even woke up. I was about 8 when I saw 'Robocop' (thank's to my much older brother having a pirate copy) and that kept my attention. So that does seem to be about the right age for kids to develop an attention span longer than 5 mins.
That said, I showed my nieces and nephew 'Spirited Away' when they were variously in the 4-7 range and they were all utterly entranced and *silent* for the entire two hours, to the utter astonishment of their parents!