Do you assume people would be spending their BI rationally? Spending everything on gambling and drugs would still be possible, having more than the least possible income by shady means would still appeal to some. It seems to me reasons for crime wouldn't be exactly destroyed.
If BI was disbursed bi-weekly, then "Spending everything" wouldn't be a catastrophic failure. It's not like you'd be sitting on a pot of gold. What if BI was disbursed daily, even? You would never amass enough money to "spend everything" on gambling on drugs...
Irrational spending of BI is not relevant. One could have irrational spending of your own salary as well. Thats not the problem BI tries to solve.
Theres always going to be money crimes as long as there is money, but its very different to take a risk on your monthly stipend to get 200 bucks. Its just a huge economical incentive not to do it, particularly in the lowest class, where violent crime is concentrated.
Gangs, Mafia's and drug organizations are based on a worker class that is super cheap to them, those out of poverty and desperation. It would deal a major blow to everyday regular crime.
