The form of a Petrarchan sonnet standardizes his work. The rhythym of 10 syllables per line turns it into somewhat of a song. The 1st eight lines are the octave , which are the introduction. Then the final six lines are the resolution. The turning point is the volta, which is at the beginning of the sestet.
In order for him to stick to his standards of writing within those formats- he may have been limited in what words he could use to get them to fit into the 10 sylable format. That alone could affect the content.