What is the reason why ancient poems need to rhyme?

Rhyme is determined by the genre of poetry, and poetry is a kind of verse. It can be said that all rhymes can be called poems, but each has its own advantages and disadvantages. Poetry is short in genre and concise in content, and rhymes in order to be more fluent, easy to recite and easy to sing. Rhyme is rhyme and verve. If people talk, they are healthy, full of enthusiasm and fluent and sweet, others will like to listen. If you are sick, suffering from tracheitis and tuberculosis, and speak weakly and intermittently, others will feel uncomfortable. The ancients paid attention to it, and after constant exploration, induction and summary, they understood that rhyming is better than not rhyming, so the ancient poems after the Tang Dynasty basically rhymed. This is an improvement. However, there are many poems that don't rhyme, such as "A Short Song Line", "A Bitter Cold Line" and "Youzhou Tower", but they are all famous ancient poems. It can be seen that whether poetry rhymes or not can still be discussed, and it cannot be killed with a stick. Poetry seems to have an internal rhythm. I don't understand. Let's stop.