I do power lifting. I'm an advanced lifter (but not quite competitive levels) for my weight class and age. I e.g. deadlift 180kg raw (without equipment/belts etc.).
Yet carrying my 25kg son around gets exhausting after a few minutes, and that's when he's cooperating and holding on. I can do it for quite an amount of time, but not without being a wreck afterwards.
Most people don't have the strength or endurance to carry 30kg of dead weight around for long in any position, but more importantly, even if you can carry 30kg around on your back or clutched to your chest, does not mean you are able to do anything useful with that weight, such as being able to lift it up to chest height and push it into place, or rotating it to slide it into awkward spots, or any number of other things.
E.g. being able to overhead press 100kg still means I'm just barely able to safely push a 30kg server into place high up in a rack without assistance - precision movements or moving into positions that affect your balance or leverage in any way very substantially reduces the amount you're able to lift.
Increasing the amount of time you can carry a weight around, or increasing your ability to move the weight into various positions alone will be a big deal.