People are not corrupt, but they are survivors.
The culprit is the unjust system, because of which a vendor/employee do corruption to make ends meet, while the buyer/customer present bribe knowing that his task won't be done without bribing someone. This change of mindset happens over generations of unjust system and will take generations again to change it.
Just for example : The same Pakistani people who cross red light for pleasure(or without fear), wear no seat belt, follow every traffic rule when abroad because they know they won't be able to bribe through the violation.