I suspect the main problem is cost. I have a full set of Kennon
cabin, cowl, wing, and elevator covers for mine, and before I found a
reasonable hangar used the covers year-round. I can see the
difference on the finish between covered and uncovered areas. I still
use the wing covers in the hangar since the roof leaks.

Pros
1. In winter, keeps the surfaces ice free.
2. Protects from dirt and UV - paint holds up much better.
3. Keeps rain out of the tanks and interior.
4. Tail cover keeps birds out of the tail cone, cowl cover keeps
them out of the engine.

Cons
a. Additional capital cost
b. Time to uncover/recover. Putting covers on can be a pain when
it's windy, though you can develop techniques to help.

My overall opinion is that the covers are an excellent way to protect
your investment. Don't use nylon, though; go with the canvas covers,
as they breathe better after it rains.