Here is why it does not equalize taxes, especially for incorporated professionals: 
 School to become nurse, paramedic, medical technician, dental technician:  3-4 years. Cost about 25K per year. Start work at 6oK, upgrade to eventually make 90-120K after 6-10 years. Doctor, dentist, veterinarian, law for 7-10 years cost 25k per year for first 4 years 25K, rising much higher once starting professional training. 35-70K per year, assuming additional 4 years about extra 200K. Start job residency or "new vet" or associate at 50K -80K for next 5 years.  Then (if dentist or vet) invest 500K+ to open practice and don't break even for another 3-5 years. After 15 years finally making $200+, an magically enter top tax bracket with no consideration for extended period of minimal income. Technicians way ahead financially for first 20 years.