Ultrasound technicians

I had an ultrasound at 12 weeks and 15 weeks. Both times I asked if they could tell the gender. Obviously at 12 weeks it was a long shot but at 15 is when I found out with my previous pregnancy. However, both times I asked they refused to even look! Just responded with “nope it’s too small” without an attempt at a glance. Yes I know that they can’t for sure determine until 20 weeks but what’s the harm in looking? My question is for anybody in the medical field who would know...is there a new rule that they aren’t supposed to tell you because of the margin for error or are my techs just not willing because that’s not what I’m there for?