4. Anything Sony makes requires different adapters, different batteries and different memory cards than the rest of the market.

Diversity, variations, mutations -- whatever drives "evolutionary systems" (such as markets) has such side-effects -- with many overwhelmingly "positive" consequences too, though.

"why do we need" -- nobody said we do. What you don't need, you don't use. Easy.

Actually for number 3, assuming you're talking about the mini usb and the square type USB, I'd say the miniusb is better for smaller gadgets. So it wouldn't be ideal to put a regular USB size connector on all types of gadgets.

Ipod's dock connector is wide so it can physically stand the ipod, iphone, or whatever up when plugged in. So the physical design of connectors often serve purposes other than just to transmit data. And for this reason we'll probably always have proprietary connectors.

You didn't mention micro-usb. I have within one meter of me, devices that require USB type A ("regular"), USB type B ("square"), mini USB, micro USB and an iPhone.

Actually I meant micro when I said mini. I'm not even sure what miniusb is.

Mini and Micro USB are similar but different:

http://en.wikipedia.org/wiki/File:Types-usb_new.svg

I've got various Card readers, HDDs, Hubs, etc. that take Mini-USB B, but I've never seen Mini-USB A or any of the micro ones in the wild. Apparently Micro USB will be used for charging mobile phones henceforth.

#1&#2: One reason is money has already been invested in tooling, so if everyone stops using connector A and starts using connector B, connector A will drop in price (down to cost of materials+labor) and someone will say "Why are we paying twice as much for connector B?" This goes for metric vs imperial, power supplies, rotors, wheels, and so on

#1&#3: If you come up with a new design, you get royalties if others use it and you don't have to pay royalties to someone else.

Because people have learned to live with them and the pain they cause is acceptably built into society. None of those things provide competitive advantage or a reason for consumers to switch.

For instance, few electronics travel outside the country where they're sold, and even for devices that do travel like cell phones or laptops, it's still easier to just buy an adapter than to choose a model based on its charging characteristics.

If something weird happened, like we all started being like Quantum Leap and the room we went to sleep in teleported to a new country every night, then the international plug problem might be worth fixing. But people would still probably just buy adapters as a cost of doing business and count on batteries to get them through the day. It just adds so little value.

It would be stupid to include a $50 dollar power supply with a $20 switch. You wouldn't want to try powering your laptop with the $2 power supply that comes with your switch.

well you can still have different levels...but take cell phones for example, you have a thousand different cell phones and each of them uses a different adapter.

I'm not even complaining about the actual power supply, I get that it varies, my complaint is that you can't use the same exact power supply(look identical) because the end part is a tiny bit different.

Future is bright in EU regarding this matter: http://www.reuters.com/article/technologyNews/idUSTRE55S1XZ2...

For that matter, why did Apple have something like 8 laptop display adapter standards? (before, to their credit, apparently setting on one)

Again with the uncommented downvotes.

Q: why are so many products in life have so many seemingly pointless variations? Answer: Capitalism.

Under alternative social structures like communism you tend to get only one option for any particular product as more than one option is wasteful unless it has significant variation in function.