Ol' Phil liked form, and lots of his poems use rhyme and meter. While "Toads" takes a less traditional approach, form still plays a part. (For more on this, check out "Form and Meter.")
The bleak, "resigned to a life of misery and failure" vibe in "Toads" is present in many Larkin poems. It was kind of his thing. After all, he's the guy that famously said, "I think writing about unhappiness is probably the source of my popularity, […] most people are unhappy, don't you think?" Phil did have a sense of humor, but it was definitely on the dark side. Okay, "humor" might be a little strong. None of his poems are really ha-ha funny. They're more the "Um… I can't believe he said that," kind of funny.