Why do people use mortgages, when they could just pay for the house in full?
Some countries, like the United States, allow a mortgage interest tax deduction.  This means the interest you pay on a mortgage, which is typically much more than half of the monthly payment at the beginning of a 25 year mortgage, is tax deductible, so you might get 33% or more of the interest back, and that effectively makes the interest rate significantly lower.  Therefore you are borrowing the money really cheap.  That makes MrChrister's answer even more appropriate.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Why do people use mortgages, when they could just pay for the house in full?

### Response:
Some countries, like the United States, allow a mortgage interest tax deduction.  This means the interest you pay on a mortgage, which is typically much more than half of the monthly payment at the beginning of a 25 year mortgage, is tax deductible, so you might get 33% or more of the interest back, and that effectively makes the interest rate significantly lower.  Therefore you are borrowing the money really cheap.  That makes MrChrister's answer even more appropriate.