The answer to 'why is my stone walkway thin grass' is that thin or sparse grass on a stone walkway is a common issue caused by a few different factors. The main reasons are typically lack of soil, compaction, or inadequate sunlight reaching the grass.
Stone walkways are often built on top of a compacted gravel or sand base, which leaves little room for soil and grass to thrive. The weight of foot traffic can also compact the soil over time, making it difficult for grass to grow. Additionally, the stones themselves can block sunlight from reaching the grass, especially if the walkway is shaded by trees or buildings.