Why does "Copy" replace stuff instead of merging it?

This is started to be really annoying to me

If you have an original folder with 2 files and you copy something into it's parent folder where the folder name is the same, and, let's imagine you are copying 3 files and at the end you want to end up with 5 files, let's make an example, like:

Original:

~/User/abc/Documents/locale/fileA
~/User/abc/Documents/locale/fileB

Stuff you want to copy:

locale/fileC
locale/fileD
locale/fileE

When you copy it into ~/User/abc/Documents/ you get this:

There is no option to COPY / MERGE ! if you press REPLACE you will end up with:

~/User/abc/Documents/locale/fileC
~/User/abc/Documents/locale/fileD
~/User/abc/Documents/locale/fileE

instead of

~/User/abc/Documents/locale/fileA
~/User/abc/Documents/locale/fileB
~/User/abc/Documents/locale/fileC
~/User/abc/Documents/locale/fileD
~/User/abc/Documents/locale/fileE

What is going on here? How can I simple merge the stuff I want with the existing one. Like Transmit asks

Solution 1:

We (the OS X users) have been asking ourselves that question since the age of dawn.

Very well phrased question to a sad response: OS X doesn’t do that and can’t do it without 3rd party tools.

Of the 3rd party alternatives there are a lot, I’ll just go ahead and recommend what I think it’s the best alternative to Finder, but… your mileage may vary.

Path Finder by CocoaTech is not a free alternative (far from it) but it definitively addresses most of Finder shortcomings and adds a lot of nice things for the same price.

If you feel more adventurous, you can go ahead and see different alternatives and their prices right here.

Update: Back in September 2010 TotalFinder didn't exist, but it's a very nice add-on that brings Tabs, Cut, Folder Reorder, etc. to the Finder. Not free, but way smaller than Path Finder if that's what you're looking for.

Let’s hope that 10.7 brings a new paradigm where questions like these are not relevant anymore :)

Solution 2:

I believe it's because of Mac OS X way of handling certain packages.

For instance, an application. To the user, it's just an .app file, you double click it and it opens the app.
But really, it's a folder with .app extension, with a hierarchy like this:

You can see that for yourselves by righ-clicking the app and choosing "Show Package Content".

The only reason I see for Apple not to allow merge on folder is that they didn't want to confuse the user. Like asking to merge when all you want is updating an application.
And since it's a standard way to represent packages on a Mac OS X system, they didn't bother trying to differentiate between packages and simple folders.

Solution 3:

Most probably too late for all your replaced files, but copy the folder (Option ⌥ + C) and then paste the items (Option ⌥ + V), it will then ask to merge