Many builders of new houses specify only two coats of paint on new plasterboard. They do this to cut costs, and because they often get away with it. This does not meet AS/NZS 2311 – Guide to the painting of buildings. It can mean that the paintwork will have lower durability, or worse still, that no sealer is applied, leading to pre-mature paint failure.
The standard for painting requires a minimum of three coats on all new unsealed surfaces, unless the manufacturer states otherwise. The first coat must be a plasterboard sealer, to seal the plasterboard joins, and the plasterboard. The following coats should be top-coats; that means they offer a level of washability or scrubbability. Ask to see the builder's specification before you sign any contracts, and make sure it meets the requirements of AS/NZS 2311 – Guide to the painting of buildings. If it doesn't say three coats, there isn't much you can do about it after the day of handover. Make sure the specification meets the standards, and ask for a variation if it doesn't, before you accept hand-over from the builder.
Another common practice is to use matt paint on walls. This is used to hide imperfections in the plaster. It might look ok at first, but matt paint does not have the washability or scrubbability of low-sheen paint. Insist on low-sheen paint for your interior walls.