The pressure in the vessel or bottle is too high for consumer devices, and furthermore it is not a constant pressure (depends on the ambient temperature). Therefore it is of extreme importance that there is a regulator right after the valve. The regulator will reduce the pressure to, for example, 1 kg/cm2. However, each device needs an additional regulator. Most devices operate at a very low pressure, varying from 30 - 50 gr/cm2.