They're too busy jacking off to fix it.
I thought it was just a problem with the 60fps when using 3D, but once I started noticing the slowdown when not using 3D, such as in horde battles, I decided that it was unacceptable. So they can do 60fps for one-on-one with some slowdown (okay, a lot of slowdown, so I guess it doesn't really count as 60fps any more, but anyway) but they can't do a solid 30fps? Bullshit.
Also, the 3DS hardware sucks dick, so there's that. Nintendo makes fucking fantastic games (at least, usually), but they CANNOT make hardware. Hell, the original 3DS essentially destroys itself. The raised edge around the touchscreen will eventually dig into the plastic on the upper screen.
The triggers stopped working on mine and I had to replace them, but one of the screws had its head strip the first time I opened the 3DS up to check them (and I do a lot of this stuff, so I don't tend to strip screws, since I know how to handle them), so when I went to open it up the second time once my replacement triggers arrived, I couldn't turn the screw at all. In the end, I had to break the screw post to get the damn thing open.
Now, my SD card slot is playing up and often doesn't read the SD card properly. Sometimes reinserting fixes it, sometimes I need to restart.
Also, the thing takes a million hours to boot up now.
Piece of crap hardware.