Noone writes Haskell like that. People generate Haskell like that because layout syntax is a fickle beast to generate and outputting braces means you can make mistakes in layout without breaking things, the way the braces and semicolons are output emphasise how they actually don't matter, they're also easy to delete in a text editor.

Also it matches up with other Haskellisms, e.g. lists:

let foo = [ bar
          , baz
          , quux
          ]

See how it's immediately apparent that you didn't miss a single comma? It's also trivial to match up opening and closing brackets like that, even in deeply nested situations.

Not doing that is actually my main pet peeve with Rust's standard formatting.