I don't know why you bother on the bus... who knows what input they will send to the flying controls from one second to the next!
(FWIW the 767 does the same - preflight procedure is to get a clearance to pressurise the hydraulics and do a control check)
Why on the bus do you need to do a brake check when you taxi (like a cessna 172) - is it because you are checking the hydraulics ? Or you are checking the computers are sending a signal to the brakes?