It must be "personal taste" or something akin to that in the reader because Oliver consistently pulls at my heart. She does so without the stilts of human tragedy and without begging the reader. I cannot read her Fox poem or her cricket poem or the song of the happy maples singing in the rain without the words reaching in and releasing an almost exultant hail of breath.
I have just two of her books (West Wind and Winter Hours) and in Winter Hours, dedicated to her life partner, Molly Malone Cook, I found Oliver's explanation. She writes in her forward to The Swan:
Years ago, I set three "rules" for myself. Every poem I write, I said, must have a genuine body, it must have sincere energy, and it must have a spiritual purpose.
Oliver has added other expectations in her 40 years of writing: she wants every poem to "rest in intensity," and to be "rich with pictures of the world." More particulars: her poem needs to ask a question and leave it unanswered. "Make sure there is nothing in the poem that would keep the reader from becoming the speaker of the poem." All her poems have been written outdoors, she says. They aren't lectures.
Often Oliver is a incantation of Whitman for me. He's another who joyously romped and wrote: I think I could go & live with the animals, they are so placid and self-contain'd. And he admonished his readers in a vein similar to Oliver when he took to the open road, out of the library, away from books, light footed and light hearted. Oliver's no different.
When I was in college many moons ago, I met a young man who was studying law. He was a parlour maid to the law library, turning pale and chubby and withdrawn. We, my friends and I, sought to bring him out of his myopia. One offered him a hit of windowpane. No, half a hit. He accepted. What happened to the pale law student? Epiphany. "Books books books," he said, and walked outdoors. I recall him often.
... and just so I'm understood: I'm not advocating acid as a way to see. Simply telling a story where that worked as a catalyst for one person. I'd much prefer walking outside and watching a chameleon as a means of sight.