You need a license to run a barber shop or hair salon because there is the very real chance you may come in contact with human bodily fluids (i.e., little nick with a razor) or parasites (i.e., lice), and you need to know enough about infection control to avoid spreading diseases from one client to another.
If you're just getting a buzz cut or trimming a little off the ends of long hair, sure, there's not much need to pay someone else to do that for you. But, quite a lot of people like to get their hair cut or styled nicer than that (not everyone looks good in a buzz cut or with long hair).
If you want to cut your own hair at home, go ahead and do so, but there's really no need to criticize other people for keeping someone employed doing it for them. If that's what someone wants to spend their money on or finds it something they enjoy, what business is it of anyone else what they do with their money or time? For that matter, you could choose not to cut your hair at all.
Since you've been starting a bunch of threads on cutting down the time and money it takes for things like eating and haircuts down to the bare minimum, there must be something else you would like to make time for doing and save up the money to do that spending time and money on these other activities distracts from. You may find that not everyone shares your enthusiasm for whatever that activity is and would consider THAT to be a waste of time and money. It all comes down to personal preference. It's fine to discuss these differences, let's just try to avoid being judgmental of other people's preferences.