In some places in Common Lisp, a series of forms are evaluated in order. For instance, in the body of a defun or lambda, or the body of a dotimes. In those cases, writing multiple forms in order works as expected. In a few places, however, such as the then and else parts of an if expressions, only a single form is allowed. Of course, one may want to actually evaluate multiple expressions in those places. For those situations, some kind of implicit of explicit grouping form is needed.