How to change default drag and drop behavior on OS X?

When you drag and drop a file in Mac's Finder, it moves the file by default. To copy the file(s) you must hold down the opt-key while you perform the action.

I found myself in a situation where I have to copy a lot of files, and it doesn't feel very "superuser" having to hold the opt-key down for the whole time. Hence, my question is if I can change the default drag and drop behavior to copy instead of move?

The default to move between drives is to copy, so if you have a sufficiently large external disk (or you make a sufficiently large disk image), you can copy in and out without holding option.

Otherwise, no. I have never heard of a way of changing that default, as it has been the same since the Classic Mac OS in the nineties.