It's just a smart move to have the API your webmail uses be a "standard"... I don't understand why i should implement Fastmails web API, when there are severa

It's just a smart move to have the API your webmail uses be a "standard"... I don't understand why i should implement Fastmails web API, when there are several major protocols that are supported by a huge ecosystem already: IMAP, CalDAV, CardDAV.