But what if I want a faster horse?

The TikTok-ification of advertising supported platforms is terrible, but makes sense to me. LinkedIn pivoted from making money on subscriptions and fees for job postings to ads, which mean the leading drivers are 'engagement' e.g. time you spend doom scrolling on their platform. This will end in disaster for the platform as a place to find jobs or employees.

Netflix I understand much less. They make money from subscriptions. If you perceive having a fantastic experience on the site by just going there, finding something you enjoy watching, and leaving... they win. Why they would foster a doom-scrolling experience I really can't really explain, other than imagining some dark pattern like they have to pay per view and want you to watch C grade movies? More time spent looking for something to watch means less time streaming?

I don't get it.

This is strongly in tin-foil hat territory but: streaming video costs a lot more money than streaming some JSON to populate a UI. Every minute you spent browsing the catalogue over playing a video is probably a significant costs saving for Netflix.

But they play those previews automatically... and that's still bandwidth used.

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.