Nesting on the ground leaves these birds incredibly vulnerable to predators which is why they have evolved ways to go undetected. One of these is some of the best camouflage in the animal kingdom, another is extremely well-hidden nests.
This strategy of concealing eggs was highly effective for ground-nesting birds long before people became part of the landscape. However, because their nests blend in so successfully with their surroundings, humans may unknowingly come too close, accidentally scaring the birds from their nests.