Scenario: You might have a good, warm, water-tight home that is exquisite for your living needs including food, drinking water, and shelter from the elements. Such a perfect place for you is a perfect place for a variety of animals also. One particular species of wildlife that loves to help your house be their house is a raccoon.
Raccoons are nocturnal animals and prefer to make their homes in your attic, it is rather dark, completely protected against heat and frosty, clear of thunderstorms and rainfall, and it is quite comfortable for them.
You, however, aren't very comfortable having uninvited house friends of the untamed canine kind, and who could blame you?