[YeGoblynQueenne]

Like I say in another comment, machine learning took off in part as a way to avoid having to hand-craft rules for expert systems' rule bases (although machine learning existed as a discipline from the early days of AI). So a lot of work on machine learning in the '80s and '90s went to learning rules.

For instance (also in another comment) Decision Tree learners basically learn a set of If-Then-Else rules. They're one type of symbolic machine learning and there's more where they came from (e.g. Ross Quinlan's FOIL, for First-Order Inductive Learner, which is basically a first-order version of decision trees; Inductive Logic Programming which I study for my PhD; and many, many more). This work has dwindled, but it's still going.

So, no, you don't have to write rules by hand, anymore than you need to set the weights of a neural net by hand. You can just learn them.