My understanding is that part of the reason this is done, is that you can buy the external PSU module pre-certified for whatever country you need to import the

My understanding is that part of the reason this is done, is that you can buy the external PSU module pre-certified for whatever country you need to import the product into. If you integrate the power supply into the inside of the product, then you need to certify the product itself individually once for whatever standard, and potentially for each country you import into. Hence Apple can do it partly because of a combination of scale and margin, where-as it's a lot harder for smaller manufacturers to do so in a cost effective or reasonable way. Having said that, I agree with you, external PSUs drive me nuts. And I love products like the Mac Mini that have it integrated.