In short, everything about color has a psychological meaning or response: https://www.ncbi.nlm.nih.gov/pubmed/28612080

Oversaturated images tend to grab our attention and there is both a trend for them and backlash as far as art is concerned (Why are vibrant, saturated photos considered 'not as good'?).

But, Social Media is not art, it is all about getting attention. Your average instagramer tends to bump both color and saturation because, to them, that pop makes the image "look better." And, for most images, they're not wrong. A little pop can go a long way to hide poor composition or to use that psychological trick to grab attention. But, at some point, it's putting lipstick on a pig.

For your artistic photography, color and the saturation of it should be used to help evoke an emotion or set a tone for your image. There are times when over saturation helps you to do that, up to and including such saturation that you end up getting colors that are unnatural (https://www.smashingmagazine.com/2009/04/the-disturbing-beauty-of-oversaturated-pictures/). And that is fine! All of the elements within your images should affect the story and emotion, including the color, contrast, and saturation.

With movies, the color palette is used for that same reason: to set a mood or theme. There's a good overview here: https://www.studiobinder.com/blog/how-to-use-color-in-film-50-examples-of-movie-color-palettes/

Another interesting example of high contrast and color saturation (although applied in selective color) is Sin City (https://www.tboake.com/443_sincity_f07.html)

Think of a movie as just a series of connected photographs. What story are you telling? What emotion are you trying to evoke? The use of colors will help tell that story. As far as color saturation is concerned, there is no rule that cine has to be less saturated and, indeed, there are many examples of highly saturated colors in movies.