With syntax highlighting being ubiquitous, does it really matter whether the keyword is "function" or "fn"? And at that point, why not make it terse instead of taking up more space and adding unnecessary noise?
`foo(){}` is just as clear as `fn foo(){}`
There is no need to distinguish between functions, modules classes, lambdas, or whatever.
Hence, no need to distinguish their start or ending with keywords, as long as you can determine their scope.
Brackets determine scope, and unlike indentation or words, that is all they are used for.