An imagery I like to use to describe the Church is that it is a place where the sick gather.
The Church is where the sick are welcome and therefore gathered to be with others who are also sick. What better place than this really, right?
Where the sick gather, sickness may abound but sickness also disappear as the sick listen to the wise words of the Doctor. The Place, however, will continue to attract the sick, and therefore, will never actually ever be free of, well, sickness! There will always be weeping, sometimes unfortunate quarrelsome disputes, violence (please), mishaps, anger, misunderstanding, visitors, and you name it. Sounds familiar? Yes, those are all sin!
So, is it any surprise that there are still sinners in our churches today? Well, the Church is a place meant for sinners to come.
Now, whenever any of the above (aka “sin”) happens, it would need to be adequately pointed out and addressed — but these things will continue to happen until there is no longer a need for the Place (which I believe is when the Son returns).
Below is a blog post from Tim Challies (I read many of his writings). I think he puts it really well to show how we are to see this “sickness” phenomena at church (read: why do Christians do still sin?):
We must distinguish between the activity of sin, which is true in all believers, and the dominion of sin, which is true of all unbelievers. Sinclair Ferguson has written, “Sin is not primarily an activity of man’s will so much as a captivity which man suffers, as an alien power grips his soul. It is an axiom for [John] Owen [whose teaching Ferguson is summarizing] that while the presence of sin can never be abolished in this life, nor the influence of sin altered (its tendency is always the same), its dominion can, indeed, must be destroyed if a man is to be a Christian.”