By keeping hydraulic pumps on you have a better chance of spotting any leaks on the walkaround and you reduce risk to ground personnel (slats droop with them off, so you then have the hassle of getting a clearance to re-pressurize). Fuel pumps? Engineers tell me they don't seem to have any less life if they run continuously, so you may as well leave them on (main tanks only!). One less thing to forget at start-up. KISS. I am talking B737 classic - no idea for 767, but am guessing same basic reasons for leaving it all in go position.