Tests are not mandatory so people do not know or do not care about the problem. Also they should be done before conceiving a child.
What tests are you talking about that should be done BEFORE conception!?
Supporting a test that says you have X gene and that might result in a problem so you can't reproduce is a ridiculous stance to have.
You seem to have no knowledge about current medical screenings and no regard for human liberty.
DNA test that detects errors (invalid sequences) known to cause serious illnesses. I think everyone who is considering to have children, should take such a test because he or she can be a carrier of invalid DNA which can be inherited and ruin life for a child. People should behave responsibly.