In most areas professional gutter systems are not required by the state on new homes, but they should be. Most contractors will just leave them off to save on the cost of material, kicking your future problems down the road. Gutters are designed to divert water from the home’s foundation. Once the water has saturated the soil enough, it could lead to foundation cracks, wall and ceiling cracking, home becoming unlevel, and many other problems.
For most of us, our home is our biggest investment; we should protect our homes as such. Over the years we have installed many "do's" and removed several "don'ts".