Half the movies released in 3D during the last wave were poorly done conversions not even shot for 3D.
Only half? -_-
I've only seen a few movies that were actually filmed in 3D. Even Gravity was filmed in 2D.
The problem is that actually filming in 3D requires using different (and expensive) hardware, and different creative direction all across the board. You can't just upgrade to a 3D camera and call it a day. Not many studios will put in that kind of effort for something that is not proven in the market. And not many filmmakers are actually skilled at working in 3D, simply due to lack of direct experience.
I saw the Hobbit movies in high framerate 3D in the theater, and while they were not good movies, they looked absolutely amazing because they were committed 100% to the format from start to finish — not just with the hardware, but with the lighting, makeup, set design, everything. It's a shame the movies sucked, and it's a shame that there has never been a way to watch them in HFR 3D outside of select theaters.

Silly question perhaps, but are you sure you're using the correct port on your Linux system? If I plug my external HD into a USB2 port, I'm stuck at 30-40MB/sec, while on a USB3 port I get ~150-180MB/sec. That's proportionally similar to the difference you described so I wonder if that's the culprit.
You can verify this in a few different ways. From Terminal, if you run
lsusbyou'll see a list of all your USB hubs and devices.It should look something like this:
So you can see three hubs, one of which is 2.0 and the other two are 3.0. The HDD is on bus 002, which we can see is a USB 3.0 hub by looking at the description of
Bus 002 Device 001. That's good.If you see it on a 2.0 bus, or on a bus with many other devices on it, that's bad and you should re-organize your USB devices so your low-speed peripherals (mouse, keyboard, etc.) are on a USB2 bus and only high-speed devices are on the USB3 bus.
You can also consult your motherboard's manual, or just look at the colors of your USB ports. By convention, gray ports are USB 1.0, blue ports are 2.0, and green ports are 3.x.
If you're running KDE, you can also view these details in the GUI with kinfocenter. Not sure what the Gnome equivalent is.