I've been using mobile internet for last few years and whenever i would try to seed it'd be like 0.2 kb/s at best. I know that it's due to my dynamic IP (or whatever it's called) and i have closed ports.
Then i saw some people say that opening your ports makes your connection better/faster because you're able to connect not only to people with open ports, but closed ones aswell. Does it make sense download-speed-wise? Because how could i take traffic from someone who's unable to seed due to closed ports?
Also, cgnat is not common in USA as there is no,shortage of ip addresses. However many other countries have hit their limits in ip4 and cgnat allows the isps to work well with more customers than addresses. Mine will disable it if you ask.
It is less common in the US, but is gaining more traction especially with carriers starting to release 5G home internet options. Currently, T-Mobile and Verizon both use it by default. AT&T has yet to launch their service but probably by/around 2024.