I have always wondered why people have to study maths for this long, esp. those who are not interested in it at all. Most of us will never care about drawing strange functions, solving their daily problems with the formula of the quadratic equation, nor logarithms and such stuff, except if you are in computing or something like that. We will forget all these things after leaving high school, and use only basic math such as addition, subtraction, multiplication, division and some percentage calculation. I don't want to offend anybody, but sometimes I think that maths lessons are just waste of time....
(Most of the points are already covered by others but...)
Let me start at the beginning.
Why do you ask that question ?
Is maths the only subject you have to learn for so many years ?
Are all the other subjects which you have to study for all these years equally useful ?
Are you asking this question because you are not
good at maths or because you are afraid of it ?
I hope thses questions help you in your understanding.
In todays world there is hardly a branch of knowledge where maths is not used.
Maths is also used extensively in all walks of life. How can people make good investment decisions ?
Calculate and pay taxes ?
Make all kinds of estimates ?
Even in hobbies : right from gardening, painting etc. one keeps coming across mathematical ideas.
But the real use of learning maths is: it helps you in developing your analytical/thinking skills.
Maths is the subject thru which one gets introduced to Logic during the school days.
Finally, If you are afraid of ( or bored / are weak in ) any subject you can assume that you approach
o that subject is wrong. This could happen due to uninspired teaching, badly written text books, or weaknesses in understanding the fundamentals of the subject. This can be overcome by seeking help from those who are good at the subject. Also try to read more about background of the subject like the history of the subject and read about the famous persons who have made outstanding contributions to it.
If you like to solve puzzles of any kind, if you like good arguments, if you like to read detective stories, you can be sure that you can learn to enjoy maths. All these will help you gain a better insight and understanding.
Don't worry too much about the usefulness of knowledge when you are young. Because this may not always have very straightforward answers.
( Reminds me of another question: What is the useof a baby ? )
For those who enjoy maths, maths is an endless source of joy.
Just learn to enjoy maths.