Everybody has slightly different boundaries when it comes to their home. While some are more than happy to entertain, accept guests, and let people stay over for any kind of reason, more people are a little more reserved with sharing their personal space. It is only fair to have some ground rules when it comes to who gets to access your living space and how; nobody would want their home to be disrespected or left in disarray because people they had over took liberties with it.
One of the more mutually beneficial ways in which we can accept house guests is when some housesitting needs to take place. The homeowner gets their plants, mail, and/or pets taken care of, and the housesitter gets a place to stay for a while. Still, not everybody is going to be comfortable having other people in their home unsupervised, even if they are trustworthy. They may want their space to remain as private and personal as possible, even if they need somebody to help them out with a few of the chores while they do not happen to be there.