Because zombies are dead and are nothing but rotting flesh how long do you think a zombie would still have enough mass and strength in things like bones, muscles and tendons?
A living human can only survive for a few days without food and water so it would only be a day or two before zombies would lose any physical ability to cause destruction.
Just lock your doors and windows and play a few computer games, read a book, cook something special and it will all blow over