Many people are not aware how complex drain cleaning can be.
as a Master plumber and having completed a 5 year (10,000 hr) and 744 hrs of class room studies I wish my training would have included the drain cleaning aspect of "plumbing" would have saved me a lot of time from having to learn by OJT
Between water jetting, rodding ,ram jets , vacuums and video inspections this profession is really quite interesting if taken seriously.
Not to mention very profitable if performed correctly.