Minimal marketing effort. Minimal quality requirements when compared to repaint. Often working in same sub division, so workers can find the site. Little protection or care required compared to repaint. Many work for wages only.
Many contractors are slow pay and string out the painting contractor.
This technique traps the painter to keep working for them at coolie wages in order to eventually get paid. Painting contractor finances builder, no upfront payments. Others damage completed paint, and builder expects it to be repaired for free. In many cases, the competition to which the builder compares you to is less professional. Some competition uses and abuses illegal aliens and the builders don't care.