When you want a license to practice, say, cosmetology, you need the permission of the Kentucky Board of Hairdressers and Cosmetologists.
Without a license issued by them, you can't teach cosmetology, own a business that teaches it, become an apprentice in cosmetology, or operate a beauty salon. Same thing applies to nail technicians. Why? Consumer protection. You can hurt someone using chemicals, or operate your salon in unsanitary conditions that could make someone ill.