Why do techs scare you?

Why would a ultrasound tech prepare me for miscarriage if my baby is 5 days behind with a high and good heartbeat for 5W5D over 103bmp at 108bmp? Why do they scare you as if it's fun? But then tell you because a heart beat was seen the percentage of that happening drops to 4%. I mean what's the point of that! Having me worry but tell me not too. Said she couldn't confirm pregnancy because heart rate wasn't over 110. I don't get it