Disagree strongly here. Memorization is a workout for the brain. Being able to recall the exact words of, e.g. poetry or prose, admits them to reflection at any time, not just when notes are available. There is no substitute for knowing something without reference; it then becomes part of consciousness, not another book on the shelf that yeah, could be opened at some point, but in practice. Your brain is weaker and emptier when you opt out of actually committing things to memory.