The ability to be used as conduits is the only purpose for the GMC A/C Hoses and A/C Pipes are on your truck. The A/C Filter has a different purpose of removing the moisture in the Freon that travels through the hoses and pipes on your A/C system.
What most GMC owners are not aware of is the relationship the filter has with the hoses and pipes in this system. Moisture in an A/C system will be converted to an acid by its interaction with the Freon. This acid will eat away at the walls of the A/C hoses and pipes causing a rupture in this otherwise closed loop system. Unlike other filters on your truck that are in place to remove small particulates from the fluid like the oil and gas filters, the A/C filter is only responsible for the removal of moisture, not particulates in the gas Freon. By this component performing its responsibility, the acid that could be forming is prevented, keeping the integrity of the lines and hoses intact for an extended period of time.
This is why it is so important if one of the GMC A/C pipes or hoses has to be replaced a new filter is placed on the system. To replace the old pipe or hose, the closed loop system has to be opened. No matter how short the period of time the system is open to the atmosphere or how well the system is closed up and evacuated, moisture will enter the system and be present on your GMC truck. This is why a new filter in your A/C system must be installed every time your GMC A/C system is opened.