I fly on average about twice a week so I have the whole safety briefing just about memorized. So while I mostly tune out because of that, I think the majority of people just tune out because a lot of the information is too obvious and most is repeated later in the flight (e.g. "The fasten safety belt indicator light has been activated. For your safety, please ensure your safety belt is security fastened and do not wander about the cabin.") It's been about ten years that I can recall a movie theater reminding me during the previews to locate the nearest exit in case of a fire. Honestly, I'd rather see the safety briefing go away and just make everyone refer to the printed handout already in front of every passenger - like with my car.
Until recently (with in-dash navigation systems warning screens) the auto industry has gotten by with using the supplemental car manuals to cover all the safety items with 98% of car owners never reading it cover to cover. I just pray the day never comes that before I drive my car, I have to watch a three-minute video on the in-dash navigation screen how to fasten my seat belt, what to do if the air bag deployment system goes off, and how there are many car model choices and Toyota thanks me for my continued loyalty and hopes that I'll drive again with them real soon. Great for catching bank robbers driving away, but horrible for escaping chainsaw maniacs and zombie hordes.