Though there are potential illegal monetary rewards for finding bugs, creating legitimate monetary bounties for bugs could easily backfire and encourage buggy patch submissions.
When Vietnam was a French colony, the government offered a bounty on rats as a means of pest control. Rather than reducing the number of rats in Hanoi, it caused entrepreneuring individuals to start farming rats.
( https://en.wikipedia.org/wiki/Cobra_effect )
The same thing could easily happen bugs.