All ground is not fertile. If you had ever seen the caliche in the Texas hill country, you'd know what infertile soil looks like!
If you place herbs in quite fertile soil (loose, lots of organic matter, fertilized) they will grow like crazy and have little taste. If you put herbs in not very fertile (still loose enough to dig in, no added compost/fertilizer, and watered sparingly) the "tough love" will allow them to grow, but the natural oils that provide flavor will be more concentrated and you will get tastier herbs.
Most of our culinary herbs (oregano, basil, rosemary, thyme, etc.) are Mediterranean in origin, where they live and thrive on thin soil and hillsides (good drainage).