Why aren't prescription medications prepared in advance? Why do pharmacies prepare them? How do they have the training to do so? I thought they simply require you to have a prescription and simply sell you the medicine and that is it?

Some . Some prescriptions (such as liquid suspensions) need to be mixed when you pick them up because they will lose strength a couple weeks after the water is added. Other times pills need to be counted. In all cases an individual label needs to be generated with your specific instructions and the pharmacist needs to verify that the medication is not something you are allergic to or something that you can't take with your other medications.