What makes Miracle-Gro so great?

A few years ago I used Miracle Gro exclusively and had fast growing plants. Oh yeah, and bugs and diseases like crazy. Not a single earthworm lived in that raised bed. I followed kimmsr's advise and went the organic material route and now the bugs don't bother and the worms are back. Compost and mulch made a world of difference. I'm especially surprised at the power of mulch and it's relationship to soil improvement.