Lam al-Amr is especially useful in these areas:
● Passive voice: third, second and first person.
● Active voice: especially third and first person.
لِيُكْرَمْ ضَيْفُنَا — our guest should be honored: passive.
لِنَدْرُسْ — we should study: active, first person.
This is a teaching distribution, not an absolute ban on every active second-person occurrence. فَلْتَعْبُدُوا is an active second-person example.