What do you think causes the crackle and clicks we hear?

Some of my favourite second hand records have noticeable surface noise even after cleaning. My 'solution' is simply to play them 'wet'. I find wiping the record with a very thin layer of record cleaning fluid or just plain water and then playing it makes otherwise noisy records, quiet and enjoyable. I've read from various 'prophets of doom' that my stylus will fall off! my records will be ruined, my hair will fall out (well that bits true). My Ikeda 'Kai' plays too near the record surface for comfort but my, bought for trying out charity shop finds, Denon DL 103 plays wet records no problem and sounds amazing to boot!