Why do we sin in Ramadan even though the devils are chained?

Allah gave us the faculty to choose between right and wrong. If a person chooses to do good, he/she will be rewarded with good and he/she chooses to do bad then he/she should expect to reap what they have sowed. The faculty to choose is given to us at birth, but this matures and ripens from the time we reach the age of puberty, and it is with us till we live this world. That faculty is with us inside and outside of Ramadan. As for Satan, he does not choose for us, he just whispers and tries to encourage us to choose what is wrong. He, however, is not responsible for our choices, we are. So, he will be punished for encouraging us but we will have to face the consequences of our choices So, as you can see, whether the devil is there or not, we still have a choice to make, so it is no surprise that even when the devil is not there we still might decide to act wrongly. Add to this: for the 11 months, the devil is grooming us so that even while he is absent: we can still act in a way that would please him. In conclusion: The first person to blame for any wrong decision is always us. Alhamdulillah, Almighty Allah has given us an opportunity in Ramadan to control our desires so that it will become easier for us to make the right choices. And Allah knows best.