The main reason that people do not write is fear of one sort or another.
They have various thoughts running through their brains such as : will my writing be good enough? Will people want to read it? Will people laugh at me?
It is the fear of exposing the workings of their private mind to the world at large, to friends and family and to all comers old and new.
2. Work:Reward Ratio.
When people want to write, one of the first things they do is to start to google various questions. just like when you want to change careers, you ask your faithful computer/Internet some basic and fundamental questions:
How do people write?
How do writers earn their living?
How much money do writers make?
And the results of these searches are often page after page of writers explaining just how little they actually earn. Warning others off trying to do the same and saying that not everyone can be like J.K. Rowling. This is an immediate dis-incentive. Why would anyone want to put themselves through that anyway?
3. Not Having Any Ideas:
The thing is, that most people do not have any ideas if put on the spot, and the thing also is that, most people would be able to come up with some amazing ideas if they were given half an hour and asked to come up with the most outrageous thing they can think of. Admitedly, there are some people who, after half an hour of thinking would imagine that it is outrageous to put paper in the normal bin and not the recycling bin (oh the terror!) but they would be few and far between.
4. Having an important career and other life.
Is it always a shock to find out that a respected High Court judge writes fluffy romances, or the Police Metropolitan Commisionner writes children's stories? I don't know. But it is possibly enough of a put off for these people to think to embark on a second career as a writer.
5. Having a silly name:
There are many people in all walks of life whose names now trip off the tongue because of the different things they now stand for. Donald Trump, something which obviously means a greatly different thing in the UK than in the States, is a prime example. How about Audrey Niffeneger, or Arnold Schwarzenegger? And a writer is at an advantage from the start because they can take a nom de plume.
6. Just Realising How Much Sheer Hard Work is Involved.
Many writers or would-be writers baulk at the idea of producing a certain numbers of coherently flowing words. Then, having written them, the idea of sitting down to edit them is also a huge put off!
But it is like playing the lottery. Why do people play for that one in fourteen million chance of winning? Someone has to win. Someone has to be the Rowling, the Tolkein, the Fleming, the Cartland, The Clarke... This list is endless!
The question should not be 'why Do people not write', but what on earth is stopping them?