Question

Why aren't there any cures for genetic disorders?

Answer 1

Because, they are embedded deep in every cell's nucleus that is in your body.
You can reduce it's effect. Even stop it at times by different types of inhibition but not permanently cure it.

Answer 2

A "cure" suggests changing the causal mechanisms for the disease, i.e., changing the nucleotide sequences. This is impractical to do (even via retroviruses) for every single cell in a human body, hence no cure.

However, there are methods to reduce a disorder's symptoms, and potentially even repress its expression.

Answer 3

That is by far a better answer.

Answer 4

Gene therapy does have some potential, despite the difficulties correctly stated above. If the cell type which is affected by the genetic disorder is accessible then getting a sequence in by transfection might be possible. Remember that although every cell carries the mutation, it is only the cells which make the protein that need to be fixed. Have a look at Gene therapy on wikipedia for examples.