Why it's designed that way is a matter of speculation, but we can probably think of good reasons for most of those behaviors:
It would be important, when moving icons, to avoid moving them unintentionally. The mouse pointer is often moving when the click is made, yet that click is probably most often just done to open the application. To have the icon dragged at that moment would be very inconvenient. A delay of some time - and a one-second delay does not seem unreasonable - to make sure that the click-and-hold is intended would prevent moving the icon when it is not intended.
The need to drag the icon to the right seems reasonable, too. Perhaps it would make more sense to you if you thought of it as dragging the icon from the launcher, and then back to it. It makes the user's intention quite clear, so that Unity is not likely to misinterpret the gesture. It might work as well just to move the icon up or down, but this way works, too.
Suggestions to change such behaviors might be welcome, I suppose, to those who develop Unity, but these actions actually appear to me to be pretty well-thought-out. After having used Unity for about a year now, both of these actions seem very comfortable. Most important, though, is that they work. You can move the icons and rearrange the launcher, and the method is not excessively complex or involved. (Why do we drive on the right in some countries and on the left in others? There are historical reasons, yes, but I don't think, in the end, one way is better than another. It's just what one is accustomed to doing.)