...older buildings, like Nparkers, were built with them not required and will never be required. I also think the drains do not always work.
While there is a pan under my hot water tank, and presumably beneath the others in my building, for whatever reason, a number of units have experienced flooding when hot water tanks failed. I do not know if there was an issue with drainage, but one owner had her place flooded twice due to a neighbouring hot water tank issue. About 10 years ago our strata mandated that hot water tanks needed to be under warranty. If not, damages occurring as a result of tanks failing would be charged to the owner of the faulty device. I doubt any owners wanted to be responsible for these expenses or perhaps worse have them charged to our individual insurance policies (the deductible alone quite likely being more than the cost of new hot water tank).