Why there is no protocol that would allow a network to request blocking traffic from a subnet or network? For example, AS X doesn't want any traffic from Y, and all operators between X and Y block traffic from Y to X.
To motivate lazy network operators, this protocol should be linked with financial conditions: an operator who doesn't honor the request, gets significantly reduced payment for this month's traffic.
I see weak people whining about attacks for like 10 years, and nobody changes anything. It's easier to blame evil hackers than fix their own broken poorly designed systems.
To give specific example, imagine a business which has 95% customers in developed country A, but receives 99% web requests from developing countries (DDoS attacks mainly come from there). It makes financial sense to cut off those countries first and after than figure out what happened.