Because the transformer doesn't have a metal case and once the voltage is lowered at the transformer the danger of electrical shock is reduced (as in the effects of it) so there's no reason to ground the laptop chassis.
That is probably why it is considered legal to sell the product, yes.
The high frequency buzzing you feel in your hands as you place them on the computer when the incoming power is not a proper clean sinus wave is unpleasant. Stoping that buzzing would be a good reason to ground the adapter even if it not legally required.
> The high frequency buzzing you feel in your hands as you place them on the computer when the incoming power is not a proper clean sinus wave is unpleasant.
I’ve used countless MacBooks over the years across several countries and even on square wave UPS systems. I’ve never experienced anything like this. This is literally the first time I’m hearing about this phenomenon.
The way people are talking about Apple products as having some sort of weird grounding defect in this thread is honestly kind of baffling, given that they obviously have built a product that complies with all international regulations around the world.
This is just how ungrounded devices sometimes act when you are able to come into contact with the neutral via some current path. I have LED light bulbs that are like this, you feel a vibration when touching the exposed metal heatsink of the bulb, and some bulb fixtures have started to be manufactured with a ground wire on the chassis just to eliminate that.
There is a reason to fix it as the comments are showing it, but yes it's not really for safety reason. It's annoying, a shitty user experience and makes it feel like a lower quality product. Even if it's a minor thing some users are still bothered by it but probably not enough to the companies to care.
