ETI is a special case - some say there is no life at all, except on Earth. They rule out any chance of life of any kind forming anywhere else in 14+ billion lightyears of space.

I like Timothy Ferris's anaology of the search for ETI with having lobster for dinner. He sets the table, unlocks the front door and waits for a lobster to show up. The analogy reveals a failure to take into account what a lobster is actually doing.