I have not seen someone miss the point on so many different levels at once in quite a while.
1) There is no pci-e power cable. You could either mean the pci-e bus connector, or the extra power connectors (6 and 8 pins) that are currently exclusively meant for graphics cards. Assuming the latter, why is a maximum of 8 pins an issue?
2) AC=/DC. Comparing a wall outlet on AC, to a PSU that runs several different DC outputs, is foolhardy at best.
3) Resistance is inherent in all wires (unless they are a superconductor). This means that too much amperage passing through it will melt it. The size of wires is set by connection standards, so that you can actually hook up a PC to other components.
4) Whining without understanding fail. This is my last point, but it will take time.
Imagine you are building three PCs right now. One is an HTPC, the other is a gaming rig, and finally a workstation for graphics rendering. Lets say you use one motherboard manufacturer, and three different PSU manufacturers. You can now hook-up extra leads to the workstation to provide extra power, but still have the same basic connections for an HTPC. That's for a good reason.
Now imagine if there were no standards. Motherboard manufacturer x, the one you purchased from, has three different boards, with power requirements that vary dramatically. You need to choose a PSU that not only meets your requirements on voltage and amperage, but meets connector size requirements. Because each board varies substantially, the amount of PSUs you can choose from per build is two. Those two PSUs can have an artificially inflated price, because there is no competition.
For those too young to remember, this is how Dell used to work. Proprietary connectors and standards made it impossible to service a PC without Dell parts, creating a very lucrative mark-up in pricing for Dell.
So, no. The idea of bigger connectors is stupid, because standards exist for a reason. If you want to change the standards you are welcome, but moaning isn't going to do it.
PS:
Chips have millions of gates. The small size is an afterthought, because the cross-sectional area is huge, which is what allows large amperages (and therefore large amounts of power) to flow.