Hairstylists at the walk-up-only places that say they do a "super" job often put caustic chemicals on clients where the chemicals don't belong and don't clean it up as they go. The client will be somewhat more comfortable at a better salon. Box color from a drug store is very mild and doesn't last as long, so DIY is not great. Hair straightening chemistry "from Brazil" is so hard-core that pregnant women feel the need to avoid the area (or salon). So not only does the required training matter, there is a huge correlation between what you pay and what it's like.
Barber combines a lot of chemicals on top of people head/face. Just because you don't see them as knowledge worker doesn't mean they can work uneducated.
Chemicals being hair/face/skin products (sprays, gells, shaving cream, creams/moisturizers) which are commercially produced, tested and sold at retail/wholesale?
Yes, they need to be knowledgable (growth patterns/directions, skin issues that may cause complications, hair-loss aware haircuts), but 3-times the training as a police officer, really? To be a Rhode Island State Trooper, it is a "grueling" 24-week program... https://risp.ri.gov/academy/trooper
Maybe prior to the 19th-century, when barbers were also surgeons and dentists that would be a minimal amount of training - but that is no longer the case.
>but 3-times the training as a police officer, really?
This is a crummy comparison, because the problem isn't that barbers get too much training (maybe they do) but that police officers get very little training.
> which are commercially produced, tested and sold at retail/wholesale?
That doesn't mean they won't kill you -> try drinking bleach or pesticides for demostic plants, both avaliable at the nearest supermarket.
Barber chemicals can give you skin burns or render you partially bilnd. That's mostly female products though, being a men's barber is typically simpler.
that being said, most of UK has no special lisence for barbers -> just need to follow health and safety and have insurance.
Not all of them are. Also, a company can sustain lawsuit differently and has access to better documentation to defend its products. Also, you're responsible to follow dosages when you apply them by your own, but the barber is when applying them on you.
Truly you should know the different implications on doing things on one own heads instead of on the head of someone else, and the difference in scale between doing it vocationally when needed and doing it all day every working day, so I don't understand why even bring the teenager example up.
Would you want someone with no experience cutting your hair?
We're in a profession that requires next to no training (except for maybe an odd "leet code" test that has no relevance to our day-to-day work, though there are plenty of jobs that don't even need that.) Maybe we're spoiled.
I've done training on handling acids that will eat right through your flesh, chemicals that make deadly gases, and how to handle biohazards like live HIV, and all were less than a day.
"they train you not to touch things? Must be super easy, don't touch the thing."
"it's super easy not to touch the thing, we have to make chemicals touch people face safely, we don't have the luxury of just not letting the face not touch the chemical"
If the instructions fit on a two pages [1] and people can do it at home with no training, I think they should be able to to cover it in a day certification for professionals.