No more ultrasound

I’m a first time mom and I only had 3 sonograms this pregnancy. When I first found out, 20 weeks, 32 weeks. I asked if I was going to get anymore and I was told no. I’m 37 weeks now. How come other doctors do ultrasounds towards the end and others don’t? Insurance thing? I figured they would to see how baby is positioned and to catch weight etc. he was head down at 32 weeks but couldn’t he still change from the position he supposed to be in?? Just curious thanks for reading.