Lighting design is two jobs: designing the show, and operating it night after night in rooms that never match the drawing.
Designing
The designer builds a plot: which fixtures, where they hang, what each one does, and a cue list tied to the setlist. It goes out ahead as part of the Technical rider, usually in a full version and a cut-down version for smaller rooms.
Operating
On tour the same person often runs the desk. In clubs the house operator takes over, working from the cue list, the setlist and whatever the artist tells them at 18:00. Hand over the set order and three sentences on the mood of each song, and the show looks intentional rather than improvised.
Costs
At club level the venue's rig and operator come with the deal. Carrying a designer means a day rate, travel, a hotel bed and sometimes hired fixtures, all of it out of the artist's fee. That makes it a production budget decision, not a question of taste.