Shakespeare's sonnets are some of the most famous love poetry ever scratched out on paper, but in Sonnet 55, the L-word is pretty dang scarce. The closest we get is waaaay at the end, in line 14, when the speaker says his beloved will live in his poem and in "lovers' eyes." So even when he does spell it out, it's not a direct come-on: not a declarative verb like "I love you, sweetie" but a noun referring to other people who love the same man.
So why isn't the speaker himself more upfront about his lovin' feelings? If you read closely, you'll see that the sonnet is actually saturated in love—not a lot of declarations, but a ton of implied feelings. Love is the reason this poem is being written, the source of the praise, and the reason that this beloved's memory will outlast the entire world.
Although the word "love" doesn't appear until the last line, this poem exists to celebrate the speaker's passion for his beloved. Good times.
Because the word "love" doesn't appear until the last line, it's clear that this poem is more about the importance of poetry than about the beloved himself. Take that, Cupid.