Tablets are supposed to be portable. Carrying a iPad retina is like carrying an iMac.
Not sure about this. a 21.5" iMac weighs 19.5 lbs. A iPad3 weighs 1.4 lbs. The mini comes in at 0.68 lbs (about 1/2 of the iPad 3).
MacBook Airs come in at 2.38 lbs and 2.96 lbs.
Comparing the iPad (any version) to a iMac does not qualify. If one is so weak they cannot carry 1.4 lbs comfortably I would get to a doctor quickly for a full checkup as there are probably medical issues here.
For me, the mini is a step back from the iPad 3 or iPad 4 just based on technical specs. There are going to be people who want it and that is fine. Just as we have different versions of laptops and desktops, we can have different versions of the tablet.
There is no need to bash a iPad3 or 4 just because one prefers the mini.