Which a CDN does as well. If a user visits the site during peak demand and the site without a CDN can't handle it, the user doesn't get the site in front of their eyeballs. With a CDN, they might. Analogy also works during DDoS attacks. Both assume that the user doesn't have infinite memory and patience to keep trying (because that's a realistic assumption).
"Amplification" has be overloaded. You are talking about a viral marketing definition, whereas CDNs are a hardware+software force multiplier for performance.