A water management system does more than just protect your home from driving rain.
A proper water management system protects from bulk moisture and vapor drive from inside and outside the home. This includes an appropriate house wrap, flashing at wall openings, and the right insulation to name just a few details.
There are many places that the durability of a home can be caused into question. However, the most important design element is getting the water management system correct. If the system is not thought through completely you could have major structural damage in just a few years.