Toyota provides recommendations for vehicles that are driven in normal service, like commuting on highways with a little around town driving. They may provide severe service recommendations, and will identify them as such. The shops with the short change intervals are giving you the severe service limits. They don’t know how you drive your car and just assume it might be severe service. I’ve followed the manufacturers recommendations for fluid changes for decades without any problems. Look at your driving conditions and decide whether it’s normal or severe and act accordingly.