This is a good constructive query and entirely logical under normal circumstances where similar poor quality methods of extraction are used.
However, lapVent is specifically designed for and ideally suit to doing the job. The complex baffle arrangements and multiple surface areas of the reservoir part of the vent body trap and collect condensing moisture, jettisoning it down onto the outer weatherside surfaces of the underfelt where it evaporates quite naturally, rapidly and harmlessly out to atmosphere without the least affect on a roof's structural materials.
Geologically, throughout the seasons, the underside surface areas of roofing materials such as clay, concrete, slate and stone remain sodden for long periods; where natural airflow between inherent fissures and inbuilt batten cavities maintain a natural balance (unless overloaded!). It is a feature that has preserved our built heritage for generations and one which lapVent exploits so confidently and efficiently - by design.