When I was a kid we had a dairy down the road that let people come in at night and take milk and leave money in a box. But milk and worms, crickets are perishable items. You can't keep them for long till they die and are useless. I suspect he didn't care because the life span for worms and crickets are short, so if they don't sell, they die and he has to throw them out. Wood will keep a long time, so if they steel it today, they can still use it months later.
You aint going to stop a crook from being a crook.
I dont know how perishable his bait was, he has outside refrigerators he keeps the bait in so it lasts a pretty good time. He's been selling bait a long time and has a pretty good setup. I would guess he keeps a check on what bait is available and just puts out enough each day to have some to sell. I also would guess he also knows who he can tell where the hide a key is.. If I need the big boxes of bait, I usually call first to make sure he has them. I have big boxes at home to store crickets in so I dont have to run to the bait store every time I want to go fishing. I know he gets fresh bait in on Wednesday's and that is the best day to get the big boxes of bait. If I run out of my stock pile, I can always drop by his place and pick up a tube or two for a single day of fishing. I usually use up my bulk buys of crickets before to many die and have found dead crickets will still catch fish. Oh the things a retired guy will waste his time on.