Why don't iptables rules work when connecting to a specific WiFi point?

Question

linux

My iptables rules deny any outgoing traffic:

iptables --flush
iptables --delete-chain
iptables -t nat --flush
iptables -t nat --delete-chain
iptables -P OUTPUT DROP

This has always worked, except recently when I connected to WiFi at a cafe nearby. When I connect to their point, the Internet becomes available to me even with such firewall rules. Checked everything several times. I deleted the rules, created them again, reinstalled the firewall itself, rebooted the PC, etc. Everything is in vain.
Then I came home, connected to my home WiFi and everything is OK, all traffic is blocked, the Internet does not work, as it should be.
Am I misunderstanding the mechanics of how networks work? Where to look, why is this happening?

Answer 1

1) Stop posting the same question
2) IPv6