I think that our readers are what legitimizes us as poets and that we owe them a little something.
If, for example, I write a stanza that rhymed ababcc, it would behoove me to write one of the following: dedecc, dedeff, ababdd, or ababcc
Something that would logically follow from the expectation I had set up.
Now, if I'm not rhyming at all -- then turning around and rhyming my last two lines might look Seussian.
Again, it makes sense, if you set up an expectation, to follow through on it.
Now, if you deliberately mess with the expectation, that is another matter and another kind of poetry and not what I'm talking abut here.
This is especially important in poetry that's intended to be heard, such as slam or lyrics. Your reader can't go back and reread the line to make sure thy got it--they are listening and if they get confused, might miss something in your next line that you're trying to say.
Note that I'm not advocating rhyming or not-rhyming or whatever. But part of the deal is communication and you can't communicate as well with someone who is confused.