Supreme court does overturn precedent occasionally, but this is extremely rare. Most of the time cases never get to the supreme court because they've already been ruled on in other cases.
Do you have any particular evidence that courts frequently ignore precedent in favor of their own wishes?
Look at the shift in law over time, which should be evidence enough. For instance, from Bowers v. Hardwick to Lawrence v. Texas, or Roe v Wade to Planned Parenthood v. Casey, in < 20 years.
As I said, it is usually the case that precedent is distinguished into oblivion rather than explicitly overruled. Only very limited technical issues are "settled law".
Do you have any particular evidence that courts frequently ignore precedent in favor of their own wishes?