What makes public works into architecture?

Public works are a broad category of infrastructure projects, financed and constructed by the government, for recreational, employment, and health and safety uses in the greater community. They include public buildings (municipal buildings, schools, hospitals), transport infrastructure (roads, railroads, bridges, pipelines, canals, ports, airports), public spaces (public squares, parks, beaches), public services (water supply and treatment, sewage treatment, electrical grid, dams), and other, usually long-term, physical assets and facilities. Though often interchangeable with public infrastructure and public capital, public works does not necessarily carry an economic component, thereby being a broader term.

Public works has been encouraged since antiquity. For example, the Roman emperor Nero encouraged the construction of various infrastructure projects during widespread deflation.[1]

this doesn't support enough information to answer the question.

answer; cultural trait;