Plumbers are the ones who are solely responsible for the fitting of pipes , finding any flaw in a water pumping motor and then going deep to provide the best possible troubleshooting techniques and if we talk in a nutshell they are managing the whole sanitary department.
Due to the dire states in many parts of the world everyone is trying to become the master of any field without having the proper knowledge of that field. We all know that a doctor or an engineer or a scientist or a religious scholar etc can't be a plumber.
It's a proper profession like many other professions that requires the particular practises,learning and experience too.
I must say to find a right plumber you need to look at his working experience if possible consult from the sanitary shops as mostly they appoint them don't go for the private plumbers who do their own work as you can't able to get any certification/ verification whatsoever.