The things they need to memorize for life are the things that serve you for life. Arithmetic is a fantastic one - you should be able to do all forms of simple arithmetic in your head, and everything to do with fractions and simple algebra on paper, and you should be able to do that stuff so naturally and instinctively that it's like riding a bike or speaking English. Because that's an ability (not just knowledge but something you can do) that will serve you for life.
Literature is a part of life and it forms how we see the world. Those pieces of poetry I have committed to memory, as diverse as "Scaffolding" by Seamus Heeney and several poems by folks like Lord Byron or William Butler Yates, inform the way I look at life.
Living is an art, not a science, and making art a part of us, for example by memorizing poetry, is an important part of being good at that art.
It's very hard to enjoy something you are forced to memorized. The things I remember in the long term I deemed important enough to keep with me. I would even say things that were drilled in me I rebelled against.
The things they need to memorize for life are the things that serve you for life. Arithmetic is a fantastic one - you should be able to do all forms of simple arithmetic in your head, and everything to do with fractions and simple algebra on paper, and you should be able to do that stuff so naturally and instinctively that it's like riding a bike or speaking English. Because that's an ability (not just knowledge but something you can do) that will serve you for life.