And tragically most users prefer the auto playing previews. Theprimeagean has a YouTube video about how he tried to a/b test it before release thinking "no way that's what users would prefer" and was unfortunately wrong.
Tbh I don't mind the previews as long as they don't make the UI lag*. I was just pointing out that they don't save bandwidth.
* I'm also aware that they're blatant lies and have little connection with what's in the actual movie.
And he is a semi popular tech YouTuber that has risen to popularity in the last couple of years. I think he also streams on twitch but I’m not on that site so I can’t say. But he worked for Netflix for about 10 years.