I'm kind of surprised that controllers designed for left handed people aren't commonplace. I've seen left handed computer mice, scissors and guitars etc. but not a lot of controllers. I'm right handed myself so it doesn't particularly matter to me, but I'm curious about why there's not a big demand for them among the left handed community.

cause the left handed people i know are used to the right handed lay out of controllers
and some prefer it that way

Well, there's not much of a problem with controllers but those fancy mouses which have extra buttons could come in left-handed versions or if they do exist, I haven't seen them.
I guess there's just not enough left-handed people to make it profitable.
I do use mouse buttons normally though, right-click is right-click and so on but my mouse is on the left.

I use my left hand to write but use my right hand to operate a right-mouse and scissors and there was no controllers for lefthanded when I grew up.

My guess is that most left-handed is "forced" to use whatever they can get, or get used to a friends right-handed mouse. And this became the norm and too few demanded it as it needs a big enough marked for investors to actually make them in big enough quanta. The only place that I have seen a left-controller or mouse is on aliexpress.

Curiously, I wonder what the real definition of left-handed is, and what criteria there is...

I consider gamepads actually better suited for lefthand people, the most important controls (directional) are always on the left side.
And for joysticks there is the T16000.M.

Probably because there is absolutely no reason why you can't use a normal controller. If you have to learn to use a controller in the first place, what difference does it make if its right or left handed? The general layout is pretty universal and shouldn't need special treatment.

like this one?
https://www.amazon.com/Razer-Naga-Handed-Gaming-Mouse/dp/B00EO2ECUY

I though most controllers were ambidextrous. Mice are a different story. A lot of their layouts plain suck even

Right hand vs left hand is an odd issue. I imagine most people are ambidextrous when you look at various products.

A few examples would be the N64 controller having FPS games aim with the left hand versus right hand aiming in modern controllers. In right hand drive cars people are changing gears with their left hand versus their right hand in most other countries. On motorbikes there were a variety of control schemes before it settled on the left side for changing gears due to market forces.

Skateboarding is another one with it's variety of stances. Steering with the right foot and pushing with the left got known as goofy yet in football most people are going to be using their right foot to kick the ball while pushing off with the left.

I am left handed but I never had any problem using a mouse, a controller or even a scissors with the right hand.

On the other side never ask me to hold a pen or a spoon with the right hand; unless you want a good laugh that is.

Because left-handed people are the devil's minions.

Remappable buttons?

True, but that doesn't mean they don't deserve to have their own game controllers.

Even useless twisted demonic freaks have rights.

If there were a market for left-handed controllers they would be produced. They take both hands anyway, so it likely nothing more than getting use to the layout left-handed or right-handed.

By "controllers", what exactly do you mean? Flight sticks? Gamepads?

Flight sticks are not really that popular anymore (outside some classic PC gamers, like many people here), but I recall some flight sticks were suitable for both hands, ie. they were symmetrical in design.

Gamepads... aren't they just as good for left and right handed people? You need to use your both hands with them anyway. I'm sure there are lots of left-handed console gamers using the gamepads just fine.

Overall, it is quite normal you have to use both of your hands anyway. Even if one of your hands is operating a mouse or a flightstick, the other has to operate the keyboard at the same time anyway. Heck, I even recall playing Mechwarrior 2 with both a flightstick and a mouse at the same time (mouse was in my left hand, a symmetrical mouse like most mice are).

Not to mention that the "fighting arcade sticks" usually had the opposite configuration, ie. the stick is in your left hand, and you operate the buttons with the right hand. I am unsure if Japanese are mostly left-handed, or why that is. It did take me some time to adjust because on PC I was accustomed to the opposite (a stick in my right hand, operating the keys (the keyboard) with my left hand).

https://www.google.fi/search?q=arcade+stick&biw=1280&bih=837&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiDyqj_89zPAhUqMJoKHS85DDwQsAQIMA

I'm using a left-handed configuration with keyboard and mouse, but with controllers except for some QTEs that require some heavy button mashing I never had many problems, it's even more practical.