They cashout before their ill gotten gains can be frozen and confiscated.
It's bitcoin poker. If you aren't cashing out your entire balance every night you are doing it wrong. Yes, people cheating/colluding and getting away with it is a concert, but 99% of the time what you are describing is moot. It's far more important to stop the behavior as soon as possible, especially when you factor in that the site will be making the funds up to the players that were affected. If they weren't able to spot the collusion, the financial penalty would be on them.
As far as the UB superuser scandal, that was an inside job. People within UB were exploiting the software to steal from the players. You can't use that as an example because here we are asking the site to looking into players colluding.
It was spotted by people in the community saying something and working together to figure out what was going on. That's what we're talking about here. It's directly analogous.
Yes the community needs to be vigilant but listing names of people that may well have done nothing wrong is not the way to go about it and if they have done something it's not the way to go about it until other avenues have been tried.
Saying "hey I saw something odd" IS being vigilant. Here's what usually happens: a dozen different people see something odd but say "oh I don't want to be a worrywort" or "I don't want to get people in trouble" or "I don't want to bother". And then one person actually makes a post about it and the dozen people all say "me too". If you see something, say something. A lot of the time it's the person not understanding how to play poker and looking dumb, but that's ok because a non-zero amount of the time what they see is a deeper problem.
Obviously saying "u r a cheater" or "u r a bot" or "this is a scam" is worthless. But if you have ACTUAL information (stats, numerous HHs, ect) you should be posting that openly to see what's up.