Most of the people talk with confidence but hesitate to write. Why?

Not every well spoken person with confidence will have the ability to write. Writing needs a lot of tools. It's a skill! You need to understand literature, grammar, know how to express yourself on paper and most importantly have your words reflect your personality and be understandable to all readers! It's not about hesitation as much as its fear of not knowing what to say or how to say it. Grab a piece of paper and throw out all your random thoughts and write in whichever way you like. Then put everything in order, replace words with more sophisticated ones and if you're able to see through the writing than people definitely will!

The main intention to speak is to express your self which can be done even if there are grammatical errors as the listeners attention is also on the core content of the speaker. 

 

Where as when it comes to writing the quality of the language, the grammar, the content everything catches the attention. The best of the writer always reviews back its writing once before finishing.  Don't we all!

this is due to weak writing skills or non involoving in writing activities.

This may be due to the language problem or may not know how to write the content

If you speak with knowledge and you know what you really mean, then you surely can write also confidently. The people who speak confidently to impress others, may lack sound insights and face problem when writing.

Secondly, yes, if you are not sure about your writing skills or grammar, you will hesitate to write.

Because many people fear writing and they do so as almost all try to give a perfect write up in one go. This is a faulty issue. Even accomplished writers can't give a perfect piece in the first attempt. The people under discussion need to start writing. Be it simple things like daily observations. This will give them confidence over time and they will be able to express their views better and confidently over time.

they are afraid! Usually people say some, some of them - a lot. When they say they are using their brain (consciousness), they give little thought to what they say, but when a person sits down at his desk, he starts to think ... and then write .... and it turns out that there is nothing to say... It is sad, but true.

In fact when we talk we tend to think less of the terms that we are going to use, but when we write we usually have time to thing of every word that we are going to write, how are we going to write it and if the reader will be able to know the meaning behind it. In addition, generally there is no problem if you speak a wrong word in a full sentence but writing a word in a wrong way can leave a bad impression on the reader. 

There is a difference between writing and talking. what one write becomes part and percel of him but if it is only to talk one can easily change or claim not to have said it only if it is being recorded.

In fact, not everyone can carry a pen can write

I agree with fadila Ghazali.The important tool in writing is grammar.What ever u write is not always right.it might make a negative impact on some.What ever u write empress your feelings and most importantly your thoughts.