Adding a subrogation waiver endorsement simply puts the identical feature directly into the insurance contract. If waiver of subrogation applies to all of the contractors at a construction site, an underwriter's exposure has not changed. It is possible to have a subrogation claim not be covered by insurance. An uncovered subrogation claim can bankrupt a contractor. Construction can be delayed due to a contractor's going bankrupt.
Many insurance policies allow waiver of subrogation if the waiver is in writing prior to the loss.
Workers compensation and commercial general liability contracts have waiver of subrogation endorsements that can be added to their respective contracts. My recommendation is that a waiver of subrogation endorsement be added to every policy for every insured at a construction site.