Your Home is not Fort Knox

• Every crack in an exterior wall, every crevice that might exist, every door jamb that doesn't seal as well as it used to can look like a giant "welcome" sign to roaches and other pests.
  
  

Roaches Hitchhike

• Anything you bring into your home can be a vehicle for roaches, from grocery bags to a box from the storage unit.
  
  

Your Home is a Climate-Controlled Environment

• The climate in your home is preferable to the outdoors for roaches. The outdoors can be wet and cold, but your home is dry and warm. Roaches find the comfortable climate of your home attractive, just as you do.
  
  

Food is Plentiful

• The tiniest crumb can make a good snack for a roach and it doesn't take much to create a smörgåsbord in the eyes of a roach. If you consider that your kitchen is an entire room devoted to food, you can easily see why a roach would want to be there.
  
  

There are No Natural Predators

• Outside, roaches can become the prey of other kinds of wildlife. In your home there are most likely no predators for roaches to worry about. Your home is safer than the outdoors so it becomes the natural choice for roaches and other pests.
  
  

Prevention

• To prevent infestations, be sure to correct any cracks in walls or doors that don't seal. Inspect everything you bring into your home from an outside source to ensure you're not carrying roaches with you. Keep food messes to a minimum in your kitchen to keep it less attractive to roaches. Set traps in dark corners, behind your refrigerator and in the back of cupboards where roaches tend to lurk.