I'll admit, when I first started torrent I was not really familiar with how it worked and how important seeding was. I would just use magnet links without configuration to save the torrent and seed after completion. Well.. I have finally, got myself back to 1.00 after a couple months and working to try to always seed double what I get for each torrent.
Often times I was one of the few random seeders available for some of these torrents. Friendly reminder to give back because you never know when you're one of the rare cases that can complete someones long lost file download!
So you are under CGNAT: https://en.wikipedia.org/wiki/Carrier-grade_NAT
From the wikipedia link:
Carrier-grade NAT usually prevents the ISP customers from using port forwarding, because the network address translation (NAT) is usually implemented by mapping ports of the NAT devices in the network to other ports in the external interface. This is done so the router will be able to map the responses to the correct device; in carrier-grade NAT networks, even though the router at the consumer end might be configured for port forwarding, the "master router" of the ISP, which runs the CGN, will block this port forwarding because the actual port would not be the port configured by the consumer.[7] In order to overcome the former disadvantage, the Port Control Protocol (PCP) has been standardized in the RFC 6887.
You will only be able to upload to someone with a public ip address or with UDP hole punch (but there are some technicalities - and doesn't work in all the cases). The same will happen if you use torrents. Maybe you don't notice difference because of the sheer amount of people using seedboxes and vpn.