This is a feature of the Finder that was first introduced with System 7. It prevents the overlapping of long filenames so you can read each icon's complete name, regardless of its length.
The Mac OS allows a long filename on an icon to run into the next spot on the grid rather than placing another icon there. The Finder skips one spot on the grid and places the next icon in the next available spot. This creates extra space between icons. The Finder does this regardless of the "Always snap to grid" choice in the Views control panel. If you don't like the extra space, you can manually place the icons where you want them. Alternatively, try shortening the name of the file or folder that is causing the gap.