You seem to paint all OSAS believers with a broad brush based on one or two bad examples. Faith in Christ is the root of salvation and works are the fruit. No fruit at all would demonstrate there is no root.
You need to realize that there may be people who believe they are saved, but are deceived. You may have people who went forward years ago during an altar call at church for example, got emotional while reciting the sinners prayer,
yet did not truly repent and believe the gospel, but were duped into believing they were saved anyway, simply because they 'recited' the sinner's prayer (as if it's a magical formula to automatically save those who merely recite those words) in spite of the fact that they
did not place their faith in Jesus Christ for salvation. Such people may live the rest of their lives living like the devil, yet say to themselves in the back of their minds, "I'm saved and will always be saved simply because I recited a prayer at church years ago." That is insanity!
I've heard numerous works-salvationists make this statement and what such people consider to be a backslidden state seems to vary from slight to extreme. ALL false religions and cults strongly oppose OSAS and teach salvation by works, including Roman Catholics, Mormons, SDA's etc.. yet 'claim' to be Christian. I see that as insanity! Those in the NOSAS camp are generally quick to unfairly label those in the OSAS camp as promoting a 'license to sin.'
The just shall live by faith and those who draw back did not believe to the saving of the soul. In verse 39, the writer of Hebrews sets up the CONTRAST that makes it clear to me that he was referring to unbelievers, not saved people: But WE are not OF THOSE who draw back to perdition, but OF THOSE who believe to the saving of the soul. Those who draw back to perdition do not believe to the saving of the soul and those who believe to the saving of the soul do not draw back to perdition.
Keep reading. 1 John 3:23 - And this is His commandment: that we should believe on the name of His Son Jesus Christ and love one another, as He gave us commandment. 24 Now he who keeps His commandments abides in Him, and He in him. And by this we know that He abides in us, by the Spirit whom He has given us.
1 John 2:3 - By this
we know that we have come to know Him, (already know Him/already saved/demonstrative evidence) if we "keep" (Greek word "tereo" - guard, observe, watch over) His commandments. 4 The one who
says, “I have come to know Him,” and does not keep (guard, observe, watch over) His commandments,
is a liar, and the truth is not in him.
1 John 3:9 -
No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God. 10 By this the
children of God and the children of the devil are obvious: anyone who
does not practice righteousness is not of God, nor the one who
does not love his brother.