Being identifiable matters more than looking smart
The purpose of a uniform on a site with visitors is not presentation, it is that anybody who sees the person knows who they are and why they are there. A parent at a school, a patient in a waiting room or a client in an office reception should not have to wonder about an unidentified adult moving through the building. Identification that can be produced on request completes that.
It also protects the cleaner. Somebody working alone in a building where they can be challenged is in a much better position if they are visibly identifiable and carrying identification. Being questioned about who you are and why you are there is unpleasant, and the arrangement that prevents it is trivially cheap compared with the difficulty of the alternative. Preventing that situation costs almost nothing compared with managing it afterwards.
