Organize blocks?

[Ataraxia]

I use Defraggler with no problems. It's helped greatly in keeping my fragmentation low. But something I see that doesn't quite make sense in my head is this picture. *see attachment*

 

Why are there so many low occupancy blocks scattered across my hard drive? There are other blocks too but, most are low occupancy. This is not a serious problem, but could be filed under curiosity. I have a 141GB Hard drive. The picture is cut off to show the last half of blocks. I read 'Understanding the Drive Map' in Piriform Docs, I'll continue to read through until I find something that helps.

 

So. Is this normal to have? Why can't these files be moved to the larger chain of blocks? Is there a way I can move those files?