They move into to attics and will not leave. They are not invited. An attic is not an oak tree, and they know this. They are too lazy to build their own homes so they try to take over someone else's. They move around in the attic at night scaring young kids and women.
Squirrels are notorious thieves, they steal food and property from other animals and people.
They are the most skilled thieves on the planet. They are hated by birds and their watchers all over. They love to steal nuts and fruits. When measures are taken to prevent them from getting the prize, they try that much harder. Squirrels assault people's gardens all over the world causing millions of dollars in crop damage.