1. Knowing something "by rote" has a negative connotation. Yet knowing something "by heart" is a good thing, right? If you memorize a poem even without understanding it, you will come to understand it later, as it kicks around in your memory. So even a "rote," non-understanding memorization, is worth-while. The alternative to not knowing a poem by memory is to have a second-hand knowledge of it.
2. To memorize a poem is to say that it is worth the time to memorize, that it is worth it. It might take half and hour, for a short poem. Then you might have to re-memorize it a few more times before it is really stored in long-term memory. Many times I memorize a poem and then never relearn it. This is still worth while: to exercise the short-term memory or to slow down the reading of a poem.
3.Learning new texts and relearning old ones, both tasks are equally worth while. At one point I knew most of a short novel by Samuel Beckett, Ill Seen Ill Said, by memory. I could relearn it if I wanted to. "There where she lies she sees Venus rise..."
4. Memorization has an oblique relationship to my "work," my published research. Obviously I don't need to memorize poetry in order to write about it. It is a technique or spiritual practice that make me what I am, rather than something that any scholar needs to do. I know scholars of poetry and even poets who don't memorize at all, who could barely recite two or three lines from memory. I don't think there is anything wrong with this. In fact, I sometimes wish I were not a slave to my own memory.