in theory, laws and policies are crafted by elected officials or experts, and bureaucrats are just the executors. but in reality, bureaucracies interpret, refine, and sometimes even reshape these rules through policy implementation. this is where a lot of inefficiency, red tape, and unintended consequences creep in.
The people writing it are not necessarily subject experts in the area and even if they were or consulted such experts they can't foresee all eventualities. So those laws would need to be constantly updated all the time which is simply infeasibly (especially in the US where the legislative branch is stuck in a near permanent gridlock by design). IMHO that would make the system much, much more inefficient.