Many atheists get their morals from their background, either directly or indirectly from family or culture, and/or from selecting what they want to do. Paul wrote:
12 For all those who sinned without law will also perish without law; but all those who sinned under law will be judged by law. 13 For the hearers of law are not the ones righteous before God, but the doers of law will be declared righteous. 14 For when people of the nations, who do not have law, do by nature the things of the law, these people, although not having law, are a law to themselves. 15 They are the very ones who demonstrate the matter of the law to be written in their hearts, while their conscience is bearing witness with them, and by their own thoughts they are being accused or even excused. Romans 2:12-15
Paul, in referring to "the law", was speaking primarily about the Law given to the Israelites through Moses. However, the kingly law that belongs to Christ applies to all who want to approach their Creator, who is the Father of Jesus Christ. (James 2:8; Matthew 22:37-39)
So those who do not acknowledge God's authority to define what is right and wrong are at a disadvantage because their choices can judge them adversely if they are not in harmony with God's righteousness.
God our Creator is still the judge, through Jesus, whether or not the atheist acknowledges them, but the advantage of knowing God's standards is that one can be declared righteous by their respect for them.
But no man is perfect, but no matter what they SAY they are, the one who respects God's standards knows legitimately what good and bad is, and they will know what to continue doing, and what to make an effort to repent from and avoid practicing.
It is for this reason that God's plan for salvation as described in the Bible is far and away the most widely distributed message in the history of humankind. This is only one indication that the real and living God is responsible for its existence, and that it is worthy of respect and study.