I've been on countless ridealongs, and on more occasions than I'd like to remember, officers had to borrow a light from me because they either weren't carrying their own or theirs was dead. One particular incident involved a foot chase into an abandoned rowhouse. It wasn't until we got in there that an officer realized he didn't have any light on him and was pretty happy that I was around to provide him with one.
I was also amazed at how many officers didn't carry spare cuff keys, or couldn't locate their only cuff key. I started carrying at least two just to make myself more "handy," which won me the good favor from a number of officers. "Need a light? Need a key? Yea, ask my ridealong: he's got one!"
I understand the bat belt gets heavy, and I really have no room to criticize because if I was doing their job, I'd probably be overloaded with a good 200 lbs of gear. It was just so foreign for me to think that some (definitely not all) guys/gals in their line of work didn't prepare for the dark, or the fact that they might need a spare cuff key.