Because a form that collects an address should say what happens to it. Nothing here is complicated, and there is no hidden part.
A name, an email address, and a message if you choose to write one. Nothing is measured, counted or fingerprinted.
Until the launch message is sent and six months after, then removed. Asking earlier is always possible and always honoured.
No partner, no provider, no advertising exchange sees a single address. The mailbox is the only place the data lives.