I.e. their job doesn't depend on them ruling the "right" way.
There are pros and cons to different approaches. There are differences at the state level for judges, being appointed vs elected. Each has problems. In TX, for example, judges are heavily influenced by mob mentality - they're afraid to practice sentencing restraint because next election their rival will run ads saying they love murderers/rapists/whatever because they let someone off lightly in extraordinary circumstances.