what is it actually for?

There are many people who work in professions that rely on ther computer for productivity. Yes, 3D animation, advanced CAD, and engineering applications can require more than 1 of those beasts to be productive.

While most people never need a pickup truck to haul around their stuff, this does not mean there is not a need for 18 wheelers.

Hm, well, apart from the creative works - if you run a lot of virtual machines then you need a good amount of RAM. Although I suppose it's rare for someone to run like 6 or so virtual machines at once

There's software developers like me who can benefit from a good amount of RAM since it makes things faster when compiling, debugging, running so many development applications, and emulation if it's applicable. Amusingly, it can be handy to have a lot when you accidentally have a memory leak or something like that - instead of bogging the system down with page-outs you can quickly detect and fix the problem since it's all in RAM.

Oh and lots of RAM is good if you do indeed photoshop large files (in the hundreds of MBs) with large amounts of layers (also in the hundreds). And this applies for pretty much everything - if you want to have a lot of undo steps, this can take a lof of memory. And you'd often want that to be fast as well.

What else is there? Just a lot of processing/rendering will take a lot of RAM. Probably someone in the scientific profession could attest to that as well.

Hmm... in any case, there's enough reason and use for a lot of memory.

Of course, anyone can work on less RAM (like 4GB?) but everything would be stupidly slow and frustrating. So it's also just nice to have a lot of RAM so that everything runs fast

mostly people would need that much power for 3d animation, scientific experiments, and maybe some very large image processing. So very few people actually need that much power, and if you have to ask what you would need it for then you don't need it.

Either you'd have to be a fool or the computer isn't being paid out of your own pocket for someone to buy the RAM from Apple or choose the SSDs from Apple.

It don't really know why you post this—there are a lot of threads on this, so a search for be quite useful. Nonetheless, people do need fast computers. Not everyone just uses their computers to just browse Facebook or check their emails. For those tasks, I can make do with my 10 year old phone.

As for the RAM and CPU, I would be able to make use of the increased capabilities. With more RAM, my Photoshop workflow would be a big faster, since I love stitching together many many pictures and working on them, and RAM would help since I wouldn't have to resort to scratch disks. The faster CPU would help my video encodings.

I don't know why people even bother with dual SuperDrives, because those drives are anything but super. If you want dual optical drives, I would get 2 Bluray drives anyways since for storage Bluray is pretty good (a little slow, but still very archivable).

Like mrkramer said, if you have to ask, you don't need it.