The conflicting needs of formatting to produce both few lines and short lines is thrown in high relief with this pattern. One extreme would be to place all the keywords and arguments on the same line, no matter how long the method. This minimizes the length of the method, but makes it difficult to read. If there are multiple keywords to a message, the fact that they all appear is important to communicate quickly to a scanning reader. Arguments do not need to be aligned, unlike keywords, because readers seldom scan all the arguments.
Arguments are only interesting in the context of their keyword.
Therefore, put zero or one argument messages on the same lines as the receiver. Smalltalk distinguishes between code which is executed immediately upon the activation of a method and code whose execution is defered. To read code accurately, you must be able to quickly distinguish which code in a method falls into which category. Code should occupy as few lines as possible, consistent with readability. Short methods are easier to assimilate quickly and they fit more easily into a browser.