Tucked away in your walls and attic mice are protected from the elements and preditors. They say 'your casa me casa'
Food & Water
No need to head outdoors with food sources and water readily available in many accessible places
But The Number 1 Reason For 'Mice In The House'
Our construction methods enable mice to take full advantage of us and most of us home owners don't have a clue or learn the hard way. Upon the foundation the brick layer forms a layer of weep holes for wall ventilation, they are left wide open. The home builder doesn't bring this up in the sale of the home because they don't want purchasers to think their house might have mice. Rather than install covers they leave it out of sight out of mind. The HVAC company installs the furnace and AC and leaves gaps where pipes pass through the wall. The Siding company installs the soffit and facia with a natural gap between the brick wall. The roofer installs the roof without reinforcing certain jointsand vents against penetration by wildlife. The Overhead door installer is dealing with in imperfect garage floor and leaves a small opening in the closed position. And the list goes on and the list doesn't address older style homes with wooden exteriors.
Wildlife Vandalism Is The Alternative Reason
It happens frequently to homes as all kinds of wildlife work away at our homes' exterior to find or create entry points. This is where many building materials and practices are not set up for success against the jaws of mice, rats, squirrels, raccoons and the like. In this case a repair is often needed with materials more suitable for the job.
You Can Prevent Many Of These Issues Before They Happen
Not all steps taken by home owners and even proffessionals from time to time are the most sound strategy and can cause other non intended consequences. One of the easiest and most effective things you can do right now by yourself is properly manage your weep holes - the most readily accessed point of entry by mice and you don't even need to get on a ladder. They are ground level. Get the solution that solves the problem for good and ensures your wall ventilation is maintained.