Registering with the sheriff can be a conundrum, as fingerprints are sent to the FBI. If a woman is known to work as a prostitute, she is subject to various social and economic penalties such as being unable to get health insurance, discrimination in housing or future employment, or accusations of unfit motherhood. In several countries a known prostitute is not allowed to immigrate or her travel is severely restricted.
I am not opposed to brothels per se. They can be a good option, especially for less experienced workers who can benefit from the shared knowledge of other professionals. But when that is the only legitimate way a prostitute can work, she finds herself with no other way to conduct business legally, while the power of third parties over her is lopsidedly strengthened. This naturally leads to exploitative circumstances. Until the needs and desires of prostitutes are fully considered and included in any schemes legitimizing our profession, many of us will choose to work illegally rather than sacrifice values important to us like freedom, privacy, and control over our work, lives and bodies.