This has nothing to do with scamming or conspiracies, but with the explanation why birthday is required.
I disagree. Lots of people my age watch only dramas and soap operas, which I absolutely hate. If you’re 3-7 years old, you might watch what others of the same age watch, but after that wiews start to diverge and it gets more difficult to guess what one would like to watch. Also Trakt has much better source for recommendations - my watch history and playlists. My age as a recommendation source can’t even come close in comparison to my actual stats.
Having said that…
This @Revenir’s post explaining/guessing things would make perfect sense, but this…
To keep showing you the best TV shows and movies, please enter your birthday.
…this is the problem I have. If I’m giving away my personal data, I want to know why, and the reason should be justifyable. In this case it’s far from such…