My 7yr old never needed the drops.
My 4yr old was very compliant but he used them after having started off without, because he wanted to get an exact prescription after noticing one eye was really very bad (she has an extremely strong nearsighted prescription in her left eye) She did need glasses.
My youngest also started off without the drops, but he could see she had a mild prescription, so again, wanted to get exact numbers so used the drops. She didn't need glasses in the end but has to go back in a few months for another exam as she may end up needing them.