If we, as readers, put ourselves inside the observing consciousness that created this poem, we immediately realize that what is said is not exactly true, that there is indeed one person on this road, Basho the Master Poet. And that the poem conveys his loneliness that no one else goes along the road. A great effect of loneliness is conveyed by remembering the poet. They make themselves manifest. Haiku is an art form which, by means of words describing the outer, gives expression to the inner.
Haiku are little working models of the unseen.
They are nano-poems whose subject is the unsayble. They generate empty space. I believe that Haiku is an artform that very plainly aims to express that which cannot be put into words. It is a way of using words to make manifest that which cannot be put into words. Haiku poems are often beautiful, but any poet who sets out to write a beautiful poem is doomed to failure.