Stress
What? You? Stressed? But you have such nice, healthy-looking hair...
In reality, being a beautician is a tad more stressful than Barbie Beauty Salon makes it seem. Barbie doesn't have whiny clients who make ultra-specific demands and who cry, get angry, and/or ask for their money back when their demands aren't met.
Barbie doesn't have to balance the books, or apply for a loan, or file tax deductibles for those new chairs and mirrors she just bought for her salon—all of which, in real-life, can be stressful, especially on top of the long, possibly-seven-days-a-week work schedule.