Squatters don’t usually go for genuinely abandoned properties, but rather ones that are empty in the short term for normal reasons (vacations, sales, grandma got moved to a home). If they went into abandoned properties then there might be repairs that need to be done, some of the utilities might not be able to be activated immediately because of connection issues, it might not be safe, and certainly the owner might not notice and then come to ask them to leave and then they would never be able to ask the owner for money to make them leave.