You being a plumber, would i assume have a totally different way of say running pipes than i would, joining pipes, bending pipes etc etc, thats what creates a mint job, the materials, the planning, the prep, the setting out, the marking etc etc, its something thats gained with years of knowledge and hands on experience.
I guarantee you that if we had identical rooms, my walls and floor would be set out differently to yours, prepped differently, and when finished would look like 2 entirely different rooms.
We dont tell you how to do plumbing mate, and anybody can do plumbing ( basic that is) same as tiling, but then theres plumbers and people who think they can plumb, then theres tile fixers and people who think they can fix tiles.