Netflix Content Rotation

I'd love to know how they work out when they take stuff off the platform and put it back on although I suspect it's probably related to people searching for things and their apparent popularity.  Have just noticed this week that a film that was on there previously is being trumpeted as being "recently added".

Still plenty of good stuff on there but have noticed that stuff gets taken off then reappears later and then they also loudly trumpeting adding 30 year old films.

And I recently found out (as I usually binge watch a series but not so fussed on films), the actual breadth of films on offer is rubbish!! lioads of rom coms/ comedies, not so much lots of recent releases/ classics ie. I wanted to watch the Girl on the train - thought that would defo be on there but nope, along wiht loads of other recent things I looked up. Why is the film selection so poor??