Because it IS about fear. Not fear of going to hell, but fear of failing to do the very basic things with God in heaven has requested of us. Even with the Holy Spirit inside of us we still fail Him on a daily (nay, hourly) basis.
1 Corinthians 3
10According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
11For other foundation can no man lay than that is laid, which is Jesus Christ.
12Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
13Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is.
14If any man's work abide which he hath built thereupon, he shall receive a reward.
15If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
YES, a believer can be saved and still do something evil. Have you ever read Romans 7
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15 [/SUP]For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.
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16 [/SUP]If then I do that which I would not, I consent unto the law that it is good.
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17 [/SUP]Now then it is no more I that do it, but sin that dwelleth in me.
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18 [/SUP]For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
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19 [/SUP]For the good that I would I do not: but the evil which I would not, that I do.
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20 [/SUP]Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.