The Row ID generated is actually a unique ID across all grids for the workspace (not all workspaces... just the one you're in.) This allows you to identify the row by ID via scripting and other things that need to reference a static ID. While it looks like it's might be useful to renumber those or whatever, noting that they're across the workspace might help understand why they are what they are.
If you want something that's more like 1,2,3, you can create a custom field for that.
Director of Product Lifecycle Management