Let's go in Spanish: vayamos vs vamos vs vamonos?
I understand that "Let's go" in Spanish is `vamonos` or `vamos` depending on the context. However, I have also learned from grammar books that all the "let's..." constructs translate into Spanish using the 1st person plural subjunctive conjugation. That's how we get `platiquemos` (from `platicar`) for "let's talk" and `andemos` (from `andar`) for "let's walk." By that analogy, shouldn't "let's go" translate into `vayamos`? Even the first person plural imperative of `ir` is `vayamos`. Why do we use `vamos` then?