In order to have torrents, someone has to buy the DVD or BluRay. If fewer people are buying that stuff, there are fewer torrents. Could be a factor? Only takes one person though for a given movie.
There is a trend now that the encodings are larger. A 110 minute movie can be anywhere from 5 to 10 gigabytes or more in full high def. Sometimes you can find newer movies in smaller sizes; sometimes not.
Downloading and storing that is inconvenient compared to streaming. It takes longer; less powerful mobile devices don't decode the large stuff very well; you may get skipping if you happen to view these huge downloads over shitty Wi-Fi in a crammed airspace.
An 0.8 to 1.5 gig download is still a reasonable alternative to streaming.
I was traveling back in January and crammed 16 movies into as many gigs of free space on the 32 gig SD card on my tablet for watching on planes and in hotel rooms. I did that by running almost each one of them through ffmpeg to get the bitrate down. In some cases I tweaked the resolution. In one or two of them, I re-coded the audio to a lower bit rate (256 kbps to 128: it wasn't a musical movie, WTF!) Almost no perceptible loss of quality; all perfectly watchable.
Pain in the butt to do that, though!
Basically, I have this theorem that two hours of a perfectly watchable movie with good sound do not require more than around 1.5 gigs of H265+AAC data. When I see larger sizes, I tend to become kind of reluctant to pull the download trigger.