I understand the æsthetic decision, but there is no reason why Apple couldn't have made the wire that runs from the brick to your laptop detachable. That way I could actually replace it for a reasonable amount.
And the replacements are quite expensive compared to the competition (I see mostly Dell and Lenovo, to be honest, no idea for the other ones).
One with the RCA/headphone power and one with the magnetic connector.
I will say, however, that the MagSafe design, even lacking strain reducers as discussed by the OP, has proven its value on more than one occasion. Besides the obvious advantages (i.e., tripping over the cord no longer sends one's laptop flying, nor does it cause catastrophic damage to the power port), I'm personally fond of the fact that you can step on the adapter all day long without damaging it. We had to replace an adapter once back in the day after accidentally stepping on the little round connector part, and bending it irreparably out of shape.
A detachable wire would violate Apple's aesthetic; thus, you can't detach it. You answer your own question.
Does Apple not replace that for free like they do the iPhone/iPod chargers?
Frankly, everything in that document just looks like common sense.
In terms of mag-safe on iOS devices, I guess it's not feasible due to it transmitting data.
This likely prevents strain by removing the probability that the cable is pulled at the strain point. It also looks cooler.
Only downside is that it doesn't untether easily; it's that the selling point of MagSafe?
Seeing everyone I know that has a macbook have his/her adapter fail, not getting a replacement and then having to buy a new one for 80 EUR I took extra care. Still the cable broke inside the connector!
I've never had this problem with any other device or notebook. Seriously, power adapters should be simple and just work - except they don't for macbooks.
Different kind of force.
Ios transfers should prepared for a disconnection anyway, it is usb, plus power failures could take the host offline.