It lies in the choice,Part 1

"Woe to her that is filthy and polluted, to the oppressing city!
² She obeyed not the voice; she received not correction; she trusted not in the Lord; she drew not near to her God."-Zephaniah 3:1-2

" Behold, the Lord's hand is not shortened, that it cannot save; neither his ear heavy, that it cannot hear:
² But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
³ For your hands are defiled with blood, and your fingers with iniquity; your lips have spoken lies, your tongue hath muttered perverseness.
⁴ None calleth for justice, nor any pleadeth for truth: they trust in vanity, and speak lies; they conceive mischief, and bring forth iniquity.
⁵ They hatch cockatrice' eggs, and weave the spider's web: he that eateth of their eggs dieth, and that which is crushed breaketh out into a viper.
⁶ Their webs shall not become garments, neither shall they cover themselves with their works: their works are works of iniquity, and the act of violence is in their hands.
⁷ Their feet run to evil, and they make haste to shed innocent blood: their thoughts are thoughts of iniquity; wasting and destruction are in their paths."-Isaiah 59:1-7


Both texts refer to filth and iniquity.
In both texts those who are sinning and those who are filthy have the freedom of choice
They choose
They choose according to their inclination

The first Scripture seems to be suggesting that the reason for the "filthiness" of this city is because they: do not obey the voice they hear,do not apply the correction-in ESV it says "she accepts no correction";does not trust in God and there's no communion between her and God-seperation.

In the second text we find an extension of what causes seperation between mankind and God-sin. 
What is sin?According to 1 John 3:4 we are told "sin is the transgression of God's law"(paraphrased) and is also defined as unrighteousness (1 John 5:17) and so forth.

But there is one underlying principle that determines whether one sins or not and it depends on the choice one makes.For you to commit sin,you must  disregard God's law.On one side of the coin we cannot stop sinning until we abide in Christ and receive strength from Him.But on the other coin,we choose.We choose,even though the Holy Spirit may convict us ofsin-we decide,we are not forced.So,on the other side of the coin,we are to be blame for our sinful ways.

James 1 tells us,
¹⁴ But every man is tempted, when he is drawn away of his own lust, and enticed.
¹⁵ Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death."

For the lust to be conceived,we still have to choose whether to give in our lust or not

Why are we still sinning?We choose to.