When someone has a cavity, not every case is black and white. Depending on the dentist's training, they may be more aggressive in treatment planning. One dentist may fill deep grooves that are "sticky," others will just monitor. Some dentists fill E2 lesions, others wait until it penetrates dentin. Etc, etc, etc
There may be dentists who are unethical but to generalize and demonize an entire profession is just stupid.