There are so many things wrong with what you're saying that i don't know where to start.
From reading of this article:
https://cointelegraph.com/news/binance-hackers-bombard-chipmixer-to-launder-at-least-4-836-btcAccording to that analyze (no one knows how fair it is but still...) only 10.8% of mixed funds are 100% linked to illicit activities (8.1% - stolen funds, 2.7% - darkn). If we consider that this numbers are true, then what do you think, would this number be lower or higher in 2016? I guess higher... Do you agree with me?
But still roughly take 10%, in 2016 bitmixer mixed 1 Million bitcoin, 10% of 1 Million is 100 000. How much bitcoin was in circulation in 2016? 16 million but at the same time 4 million is lost (according to 2017 statistics) so what numbers we got? 12 Million. 8.3% of overall bitcoins were mixed via bitmixer alone. At the same time there were very popular mixers like cryptomixer, bitblender. So a lot of bitcoins were mixed, right?
And what do you think, have people changed recently? Did they become more kind?
There have only been 2? 3? mixers that were shut down, the others either exit scammed or closed down themselves.
Great decision from owners:
About question "is a knife good or bad tool?". If you sell knifes and you know that most of your clients are murders, will you stop your business? My pastor suggest me it is not a business I should continue. Sorry for that.
No one is silly to destroy unlimited money printing machine for no reason.
Bitcoins are naturally anonymous which makes tracking the transactions a bit difficult(but not impossible) and these kind of mixing services literally make tracking the transactions almost impossible.
They are quite literally the opposite of anonymous. Every bitcoin leaves a clear "trace" which can be chained to a person on each and every offramp (exchange).
That's why people prefer to use mixer, why to leave traces to those who are going to catch me? At least make it difficult and unworthy.