I’m also poised to agree: setting the output air regulator to a low value does not change the reserve pressure in the tank. I suspect maybe Peppycito thought OP was talking about the governor, which is what controls when the pump turns on and off.

But even then, the most common design of governor only adjusts the peak reserve pressure (aka when the pump turns off) but the minimum reserve pressure (aka when the pump turns on) is usually a fixed value subtracted from the peak reserve. Usually the control for this is inside a box and turned by a screwdriver, because of how rare it is to adjust the reserve pressure.

That said, there is genuine merit in reducing the reserve pressure, if there’s an explicit objective to prolong the life of the pump as much as possible and the air loads are not very significant. But this usually isn’t the case for small residential air compressors, because those pumps tend to be built very small and thus oversubscribed.