I use car covers all the time. Sometimes, even on public lots during the day 😋
The main advantage is that it protects your car from sun. The second advantage is that you can protect the car from elements (rain outside, dust from long inside storage, etc.) and keep it clear longer.
The two disadvantages would be:
1) it can scratch the paint, if the car is dirty when covered, or if the cover is not very soft on the inside, and
2) it will trap moisture (I've seen condensation on my vehicles under the "breathable" covers.
To avoid the above disadvantages, just don't cover a dirty car, use a good quality soft cover and, if you have noticeable humidity issues, air your car out as needed
Moreover, I would recommend a cheap cover, so that you would not hesitate to throw it away when worn.
Also, very-very important: when you are buying a cover, make sure it states 100% waterproof, on it. There are plenty of "water repellent", "water resistant", "water shielding", and all sorts of other "water-stuff" covers that will actually let the water through. You don't want that, unless you are planning to use it indoors.