Some people get the impression (and there's a Barna survey that sort of backs this) that holiness isn't something we are to try to achieve. So some people get the impression that people are preaching that followers of Christ don't need to try to resist sin, or that it's too hard to reach for holiness.
And unfortunately, some people seem to believe this, even though they go to church.
And that's what some people are perceiving.
The Barna survey found:
The telephone survey of 1,003 Americans in January finds that only one-third of Americans contend that “God expects you to become holy,” and 46 percent believe God has called them to holiness. Young adults (39 years old or younger) are less likely to believe that God expects holiness
http://www.christianpost.com/article/ministries/1757/section/new.barna.survey.finds.most.americans.baffled.by.holiness/1.htm
It's clearly written that we should be holy people. Yes, we slip, but if we don't have a sense of what's sinful, or people PERCEIVE that we don't have a sense of what Jesus expects, it gets hard to be salt and light to the world.
You're right, and it's difficult to get people to hear the word by first informing them that God expects them to be holy.
I think that preaching God's love, mercy, grace, and forgiveness through the shed blood of Christ on the Cross works more to get people to be "holy" than all the sermons about sin, judgment, and holiness do.
My wife's love for me, kindness to me, her forgiveness of my stupidities, and her daily sacrifices on my behalf have done more to keep me in love with her than any amount of nagging or pointing out of my mistakes and faults could have accomplished.
With the right outlook and training, you can condition yourself to avoid sinning. (not all the time, of course, but for the most part) Even if you aren't a believer, your life here on earth will be better for it.