Consistency beats the best photo
In-house studios get judged on the catalogue as a whole. One outstanding image next to forty inconsistent ones looks worse than forty identical, ordinary ones. So the design targets repeatability: fixed lights, marked positions, written settings, the same background stock. It is less interesting to build and it is what makes an online catalogue look like it belongs to one company.
Bolt the lights down
Adjustable lighting sounds like flexibility and behaves like drift. Someone moves a head to photograph an awkward item, does not move it back, and three weeks later nobody remembers where it was. Fixing the lighting in position removes an entire category of problem, at the cost of a flexibility that in-house studios rarely use.