Why do not Booleans have a common class in Ruby?

Ruby does not have a class Boolean . I noticed that boolean objects are of specific classes depending on the value, see:

true.class  => TrueClass
false.class => FalseClass

Unlike other languages, such as C # and Java, where true and false are bool , Ruby is TrueClass or FalseClass .

This implies: if I want to check if an object is Boolean, I have to do something like:

def boolean?(value)
  [TrueClass, FalseClass].include? value.class
end

In this case, I see it as the only way to see if an object is of a boolean type. Otherwise, it would check only if an object is truthy or falsy.

!!nil #=> false
boolean?(nil) #=> false

!!"Olá!" #=> true
boolean?("Olá!") #=> false

!!false #=> false
boolean?(false) #=> true

!!true #=> true
boolean?(true) #=> true

Why was it so designed? What advantages does varying the type in question bring in the Ruby context?