Go: Why are structs "instantiated" differently from other types?

In golang, structs are instantiated differently from "regular" types:

If it's a regular type: MyFloat(2)

If it's a struct: MyFloat{2}

Is there a particular reason for this?

package main
import (
    "fmt"
)
type MyFloat float64
type MyFloat2 struct {
    X float64
}
func main() {
    f1 := MyFloat(2)
    f2 := MyFloat2{3}
    fmt.Println(f1)
    fmt.Println(f2)
}

MyFloat(2) is a conversion. MyFloat2{3} is a composite literal.

Conversions can be used on structs:

 var f3 struct {
    X float64
 }
 f4 := MyFloat2(f3)

playground