At least with web streams, pirates don't re-encode.
And since web streams are in h.264 and h.265, that's what the torrents are in too. It's not about preference, it's about the source.
(And the web streams are in h.264 and h.265 because that's what people have the most hardware decoders for, which preserves CPU usage and battery life.)
That applies for TV show. For movies though, the vast majority of new torrents are Blurays re-encoded to HEVC (x265 being the encoder used pretty much every time).
well yes, but not everyone wants to download 70GB movies, so blu-ray movies are often re-encoded for smaller filesizes (10-20GB 4K HEVC, 5-10GB 1080p H264 AC3 sound, 1-5GB 1080p HEVC AAC)
And since web streams are in h.264 and h.265, that's what the torrents are in too. It's not about preference, it's about the source.
(And the web streams are in h.264 and h.265 because that's what people have the most hardware decoders for, which preserves CPU usage and battery life.)