The reason is that rhyme is connected by two sentences, which is a complete sentence, that is to say, odd sentences must be followed by even sentences to be a sentence, and rhyme refers to the words at the end of the complete sentence, so odd sentences do not need to rhyme. In addition, unlike today's rhyme, you can ignore the tone, as long as the vowels are consistent. The rhyming sounds must be consistent. In other words, the words of the upper and lower sentences in a couplet are flat and relative, that is, the last word of the third sentence is flat and even, contrary to the last word of the fourth sentence.
Except for the first sentence, you can gamble or not.