Why, you ask? After all, many professors and teachers pooh-pooh rote memorization, citing the reasonable notion that physics is about the correct USE of fundamental principles, not about their instant recall.
As a practical matter of teaching Advanced Placement physics, the AP multiple choice section does not provide an equation sheet; thus, a student who does not know that the energy of a capacitor is (1/2)CV2 will not get a question right on that topic. (I've had it argued to me that it's better for a student just to know "energy is directly proportional to capacitance, and also to the square of the voltage." First of all, I dispute that a first or second year physics student understands what the word "proportional" means. Secondly, isn't it far easier to remember the equation than this long complex sentence?)
Beyond testing issues, I think it is pedagogically sound to insist that students know the equations that underlie the basic principles under study. Physics problem solving requires making connections between topics, using multiple intellectual skills at the same time. Students have a much easier time with multi-step problems if they have the confidence born of rote knowledge of the basic equations, if they DON'T have to spend two minutes of a 15 minute problem searching for the correct relationship on an equation sheet or in a textbook.
I make the memorization requirement clear all year in my AP class. Equation sheets are never provided, except on the free response portions of tests; students are regularly quizzed on their recall of equations. The "four minute drill," in which the class is prompted to take turns reciting as many equations as possible in four minutes, is a fun and effective rote review tool.
I hammer home the need to memorize with a final, enormous equations quiz a couple of weeks before the exam. The quiz consists of two parts: 20 prompts to which the student must write the correct equation (i.e. I say "net force" and the student replies "ma"), and 5 equations which the student must describe briefly (i.e. I say "ma" and the student says "net force"). The key is, this quiz is not graded on the square root curve -- 60% is the minimum passing score, and 90% is necessary for an A. And, crucially, a passing score is required in order to pass the course. I will have a percentage of the class get less than 60% on the first try -- these folks get to try again (with a slightly different quiz) on Monday. And probably one or two will have to try again on Tuesday. I've had seniors need four or five attempts to pass. That's fine -- since they have to pass in order to graduate, they put in the minimal effort to memorize their equations. Then they get a few more problems right on the AP exam than they otherwise would.