A 1080p video on Netflix today has lower quality (bitrate) than a 720p video on Youtube 5 years ago. The only reason Netflix HD works for so many people is because Netflix has lowered the standard of what was considered HD.
Fact is, x265 can do 25-33% smaller size than x264 for equivalent visual quality. The higher gain at higher resolutions (2k, 4k) that were not well supported by older codecs anyway. You can refer to Netflix own papers on that.
Services doing half the bandwidth have reduced quality. The improvement in codec can only explain half the reduction, the other half is grossly lowering quality (to reduce costs and work with mediocre home connections). That's not necessarily bad for customers, better have a pseudo HD stream than no stream.
Here in South Korea, 100M symmetric is the bare minimum. For just a few dollars more, you can upgrade to an "up to 500M" plan that usually provides something like 300M symmetric. Often, upload speeds are even faster than download speeds because there's less congestion in that direction.
Where was the US mentioned, and how is this relevant?
I picked the US as a worst-case example because it has some of the most asymmetric broadband plans in the developed world. How on Earth does an ISP get away with selling something like 100/5?