This may be because so many children's books rhyme, and feel like poetry, so the leap is not so great from the rhyming prose, which they are familiar with, to poems.
It is wonderful reading poetry to, and with, children.
Here are some of the poems, poetry books, and rhyming stories that we love. Please add your own suggestions.
Poems for younger children:
Tickle My Nose (and other action rhymes) Kaye Umansky
One Fish, Two Fish, Red Fish, Blue Fish Dr Seuss
Oops! Pennie Kidd
A Book of Things Freddie McKeown
Some Dogs Do Jez Alborough
Where the Wild Things Are Maurice Sendak (reads like a poem)
My Granny Went to Market Stella Blackstone
Down the Back of the Chair Margaret Mahy
Revolting Rhymes Roald Dahl
The Dangerous Journey Tove Jansson (Moomins) retold by Sophie Hannah
One Hundred Years of Poetry for Children (Oxford)
Can We Have Our Ball Back Please? Gareth Owen
Collected Poems for Children Gareth Owen
Other great poets who write for children:
Michael Rosen (check out his own performances of his poems on Youtube)