Here's why:

* Flour and water alone create a paste, not a strong adhesive. The molecules in flour and water don't bond strongly enough to create a lasting adhesive.

* The paste will dry out and become brittle. This makes it easily breakable and not suitable for most gluing needs.

* Flour paste is primarily used for temporary applications. It's often used for crafts, paper, and other lightweight materials.

To make a stronger glue, you need to add additional ingredients, like:

* Borax: This creates a chemical reaction that strengthens the adhesive properties.

* Sugar: This adds viscosity and helps the paste to stick.

* Vinegar: This helps to prevent mold and mildew growth.

So, while flour and water can be used to create a simple paste, it's not a strong adhesive. For most gluing needs, you'll need a stronger adhesive like commercial glue or a homemade glue with additional ingredients.