Check your local building code. For instance, the state of Florida mandates the installation of lightning protection systems for Hospitals (419.3.19) & Nursing Homes (420.3.26), no matter the size, location, or other criteria. An NFPA 780 Risk Assessment is required for all public educational facilities, and shall be protected accordingly (423.17.7).
Other public buildings such as, fire / police stations, EOC centers, courthouses, etc. are typically also required to be protected to meet FEMA / ICC certification.
Insurance & underwriting interests may also mandate the installation of an LPS in order to be provided with coverage.
Last but certainly not least, the design professional, developer, and/or building owner may call for the installation of an LPS.