Lesson plans are like of bullshit paperwork, invented because a minority don't do shit without being tightly monitored and a rigid structure to follow.
Good teachers can just wing a class based on whatever needs covering from the curriculum on that day, bad teachers don't care whats on the curriculum that day, terrible teachers don't care and couldn't even teach it without following a detailed plan.
Its because of those two groups that lesson plans exist.
In an ideal world you would just performance manage those two groups and sack them, but because teaching is underpaid there are a shortage of teachers (plus most people suck at putting people properly through performance management), so its beneficial to micro manage instead rather than having mass vacancies.