You have hit the nail right on the head.
There is a lot of money wrapped up in subjugating people and unconstitutionally stealing their freedom for victimless crimes, which of course aren't crimes at all.
Prisons being built is big money. Staffing prisons is big business. Prison workers unions, not to mention admin staff, service staff and other necessary workers for these institutions, is big business. Police unions, who would see a great reduction in their workforces if the drug laws were repealed, have tremendous political clout. Its a circular system of self-perpetuation. Want to build prisons and create jobs, you have to arrest people. Want to fund underfunded police operations through fines, you have to arrest people. Want to satisfy the needs of the overabundance of defense attorneys, who have a huge pro-expansion of criminalization lobby, got to arrest people.
Drug laws are nothing less than the American people being under siege for job creation to accommodate the electorate through employment. It allows politicians to go to their electorate and say "in my term we created X number of jobs." Meanwhile, those numbers are inflated by way of the persecution of people who are observing their constitutional rights of privacy and freedom without effecting others' constitutional rights to the same.