Plaster is still the most common interior pool surface (although it’s not the best). People like plaster because they’re familiar with it and it’s the least expensive of the three pool surfaces.
Most traditional plaster is white cement mixed with limestone or marble sand. By its nature, plaster has certain limitations.
Its porous surface is the most susceptible of the three to staining, bacteria growth and breakdown by the chemicals you add. Because plaster constantly reacts to water and chemicals, plaster pools “use” more chemicals to maintain a balanced water chemistry. And plaster doesn’t typically last as long as the other two surfaces (for these reasons).
You can expect a new plaster surface to give you 7 to 10 years of good service with proper care.