It can also help to align the incentives of multiple parties to actually care about the same goals.

"Mechanically preventing wrongdoing from happening" can be a bit of a Shangri-La. What Tech can mechanically do is increase the cost of wrongdoing, or temporarily deflect attempts towards easier targets. But that by definition cannot "solve the problem for everyone" as there will always be a lowest hanging fruit remaining somewhere.

What contracts can do is help to reduce the demand for wrongdoing.