Unifying fleets nobody procured together
The defining technical problem in a smart city deployment is that each department bought independently, so the estate is mixed by construction rather than by accident.
A hardware-agnostic layer ingests devices from multiple vendors into one view, which is faster and cheaper than standardising hardware across departments that have separate budgets and procurement cycles.
The alternative, replacing everything to unify it, is what stalls these projects. See the AI control tower.