A request is communication with certain semantic content, which pulling on a mailbox handle lacks. There is no general understanding among people nor specific agreement between you and some other party that pulling on your mailbox handle is how to ask you for access to your correspondence.
This is not the case for HTTP. A network protocol is an agreement about the meaning of certain clusters of bytes sent over a network. When someone operates an HTTP server, a reasonable person could conclude that they take HTTP messages to mean what HTTP says they mean. A lot of cases get more interesting because there is also something generally understood to mean, "Please don't access the following resources by automated scraping, independently of whether my server decides to grant those requests."
This is not the case for HTTP. A network protocol is an agreement about the meaning of certain clusters of bytes sent over a network. When someone operates an HTTP server, a reasonable person could conclude that they take HTTP messages to mean what HTTP says they mean. A lot of cases get more interesting because there is also something generally understood to mean, "Please don't access the following resources by automated scraping, independently of whether my server decides to grant those requests."