The Internet Commons

Spam exists because there is no cost to the sender for sending an email. The costs are borne by the Internet hosts as a whole.
The TCP protocol implements cooperation in order to avoid the tragedy:
- When a router gets too busy it simply drops packets.
- TCP resends dropped packets to ensure delivery.
- However, if there is a lot congestion, a TCP sender will postpone the resend. The performance of a TCP connection is inversely proportional to the square root of the packet loss rate.
No one forces you to implement TCP in this way.
An early example was when the first version of Netscape started to download all the pictures in parallel, effectively violating the essence of the TCP protocol...It still does.
Video streamers usually use UDP and implement their own throttle mechanisms, if any (we can't tell).