The manual tells you specific parts you need, e.g., bulbs, fuse, tire pressure, oil type, etc. It is unlikely that you have studied and remembered every details about your car.
Blankets/Sleeping Bag/Thick Coat
These are useful especially during the winter time or if you live or travel to cold places. Even in the summer you never know if air conditioning is too cold in a building.
The chance of car catching fire is probably small, but this can also be useful in case of fire anywhere, e.g., camp ground, or even friend’s house.