Adhesion is how well paint sticks to a surface. When adhesion is poor, paint peels or flakes off long before it should. That’s the main reason we spend so much time cleaning, sanding, and priming before any paint is applied.
The surface underneath does as much work as the paint itself. Grease, dust, old chalky paint, and glossy finishes all push new paint away, so each one gets addressed first. A little extra prep here is what lets a coat stay put for years, not months.