Morh
There is a huge misconception about "
health and safety regulations" mainly caused by ill informed newspapers. In fact there are very few specific regulations (on any subject) but they do include one that says any employer must risk assess any task and put in place suitable prodecures. All airlines/ baggage handling companies should have assesed the risk to staff of heaving around luggage all day (which is not the same as carrying it from the car once!) and they will have decided to put an upper limit on the weight of a single item that one person can lift. Some will have decided that if you have gone over that limit they will get two people to lift it (especially if you've paid for a Long Haul Business Class ticket) but most simply say nothing over that weight in order to make life simple. The number which most have come up with is 32kg but there's nothing to say they have to and those who have set lower limits will no doubt be able to provide a fully documented reason why.
I might say that the companies with low limits are simply trying to cut your allowance because more weight = more fuel = less profit and they are hiding behind "health and safety" as an excuse. They might say that I'm a cynic, you will have to decide for yourself!
obviously pooling within the specified limit has no H&S implication so they must have some other reason, probably to make life simple for the checkin staff.