I asked way back in the eighties about the plastic airflow shields under the engine compartment of my Volvo. The tech said they were their to protect the engine and accessories, two, improve the airflow for cooling, Venturi effect, three, a slight aerodynamic advantage on the highway.
Five bolts that I have to take off once a year to get to the oil filter is no big deal. It's the three tabs on the front of the panel that fit into a metal frame, are the real pain to get the panel off and back on. Not an issue if it's on a rack you can leave the panel hang still attached to the tabs. But if your working under it with ramps and jack stands you have to remove it to get to the oil filter.