The streaming services use fairly robust compression technology (such as H.264 / H.265) to keep each stream within a fairly compact bandwidth (6-8 Mbps is a typical target for an HD stream).
The problem is that one of the main principles of these compression algorithms is something called "motion compensation." The general idea is that only information about what changed in the scene from the previous frame is transmitted. There are occasionally "key frames" sent that represent a full snapshot with all info, usually every few seconds to sync everything back up.
https://en.wikipedia.org/wiki/Motion_compensationThe result of this is that video streams that include a lot of fast motion and a high detail background (like a grassy field with a lot of texture) have to trade off image quality in order to be able to still fit within the allocated bandwidth. It's also why you see the effect mentioned where graphics and logos look sharp (they don't change much). There just isn't enough bandwidth in a relatively constrained streaming profile to accurately convey all the visual info present in a rapidly changing, detailed scene.
A workable fix to this is to allocate more bandwidth to programs where there will be a lot of motion. I'm not up to speed on if the streaming services already do this to some extent for major sporting events but would be surprised if they don't cheat it up just a bit. Ultimately it costs them more money to do that to a large degree, so they walk a fine line between the average Joe not knowing any difference and mass complaints about picture quality.
The only real solution is to eliminate or minimize video compression, with the first not really being an option outside of broadcast-grade video production facilities where very expensive equipment is used to process and route raw uncompressed video. The best ability for a consumer to minimize the usage of compression is to view over the air broadcasts via antenna when available. These still have compression applied, but it's much lighter than streaming services and satellite TV.
