For a property with a greenbelt behind it, the useful work is narrow and specific: a garden gate whose mechanism cannot be reached or operated from the open side, a rear door anchored into masonry rather than screwed to a frame, and nothing stacked against the boundary that would function as a step. Three items, and they cover the great majority of what the position creates.
The rest of the property genuinely does not need the same treatment. Houses here overlook each other on the sides and across the crescents, and that informal supervision does real work. Spending evenly across four boundaries when only one of them faces open ground produces a worse result for the same money, and we would rather point that out than write the larger job.
Beyond the boundary, the recurring item is age. A planned suburb was built out over a comparatively short period, which means the cylinders, gate mechanisms and door furniture across whole crescents are of similar vintage and reach the end of their working lives at similar times. If your neighbours are starting to have trouble with keys, that is a reasonable prompt to look at your own.