DVDROM drive speeds

what's the difference between say a 8X DVDROM drive and 16X DVDROM drive (bar the CD reading speeds)?

since there are virtually no data DVDs, the only DVDs people use are the videos/movies. When playing videos/movies, wouldn't the drive read the disc at the same speed (8X and 16X reading at the same speed)? hence the 16X wouldn't have any advantage, would it?

i see no advantage of faster speeds, that is unless you want to rip your own DVDs