Photography vs Videography

Most of the time our clients choose both but the question is why do some only choose photography and not videography? Is it their budget? But then why photography and not videography as first choice?
I would like to hear comments about this. My personal opionion is that some are all still in "old school" where photography used to be number one choice. If I had a choice of seeing only photos of my late grandmother's wedding or a video showing all the relatives interacting and emotions I would definately choose videography. Don't get me wrong, I think you should have both but professional videography is simply no comparison.