You could ceramic coat the truck, it helps a lot protecting the paint from uv exposure.
My 20 sat in the SoCal sun 24/7 for 3 years and still looked brand new.
The plastics and rubber parts may look OK, but they do not look as nice a a truck that did not sit outside 24/7 for 3 years. The first few years, sure, not much degradation is noticable, as everything is still fresh. Paints and plastics are fuill of UV inhibitors etc. Each year that goes by though-those break down and the difference in condition widens faster and faster as well. It's not a linear thing.
If you buy new trucks on the regular- who cares right? Let the next guy worry about it.
If you plan to hold onto it though, leaving it outside is a sure way to be disappointed in it down the line. If it's black, the paint will be faded, any bare plastics will be oxidized and stained, and the plastic headlights will be sun damaged. All the rain, birdshit, pollen, and UV on the paint- baked in the heat. Water that freezes into (expanding) ice in every crevice during rain to snow events in the winter.
I've had them inside and had them outside- there is no comparison in condition after a decade, and the ones kept indoors take so much less effort to clean.