It all depends on how much calculus (tartar) you make and your periodontal health. Some people need it every 3 months with active, aggressive gum disease.
The most recent systematic review of the “every 6 months” frequency recommendation suggests that in the absence of disease, you only need a cleaning every 2 to 3 years.
No difference in oral/periodontal health status when “every 6 months” compared to cleanings yearly or every 2 years when controlling for all variables.
Just like there is no need for X-rays every visit. If you have not had a cavity in the last year, you need bitewing X-rays (in between teeth) every 2 to 3 years. Panoramic image every 5 years. X-ray of roots (periapical) taken only with symptoms of disease.
Every 6 months cleaning is a business model recommendation. No different than the prophylactic removal of asymptomatic wisdom teeth as a rite of passage.
The upside of this is that dentists never whine online about the cost of HVAC or sprinkler repairs unlike other health care professionals. Horses for courses. YMMV.