One case I've seen this, local PD, Sheriff, city Park District and county Forest Preserve District all needed access. They ech have dozens of hundreds of their own locks keyed the same, so they only need to carry one key, but they all need access to this one gate. If it was only one gate, it would be inconvenient but not too difficult, if it was a dozen shared gates, each with different overlapping agencies and each with their own key, every officer or employee would need a big ball of keys again, defeating the reason behind their keyed alike locks they already have.