People may want to participate in mixing, but then they won’t be able to get their money back in the US. It is that simple. Imagine a future where almost everyone has a Paypal(tm) Bitcoin app on their phone. And here is a bitcoin dev who has mixed all of their money. They just had a pizza with their non-technical friend, and the friend asks “Can you send me you portion of the bill? Thanks! Ugh, my phone is not accepting your payment, something about dirty money error.. Can’t you send me some normal bitcoin”? There will be no convicing that non-technical person of the problem with the “bad list”, the do not care.
In other words, you are going to have 46M people who just want bitcoin to work and don’t care about “bad bitcoin” list (US non-technical population), maybe 0.1M of principled bitcoin holders and dev who are against the mix, and 150M+ people in other countries who simply don’t care.