Why does Keats feel that the poetry of earth is never dead ?

Why does Keats feel that the poetry of earth is never dead ?

The Romantic poet Keats celebrates the eternal existence of music in the vibrant world of nature through his much focussed poem “The Poetry of Earth”. The poet, with his great sensuousness, presents the music of nature in two completely different time-frames highlighting the fact that the music of the earth continues through the seasonal cycle. In the scorching heat of summer the absence of music is deeply felt as the song-birds cease to sing, the grasshopper keeps trilling from hedge to hedge in the new-mown meadows. 

The entire atmosphere turns poetically musical again after the cold frosty winter when silence brings the symphony of nature to a halt. At that very moment the cricket starts its shrill music and that makes the drowsy man feel the warmth amidst the silence. Thus the poetry of earth continues to sweeten nature and gives all human beings sustenance.