21 weeks for anatomy?

My doctors are stubborn.. I have an 21 week ultrasound anatomy ☹️ and I don’t want to wait that long!! I see moms who have theirs at 18-20 weeks and I tell them that it’s not fair their making me wait for so long! I’ve even asked for the blood test and it’s like “oh don’t worry about the gender. You’ll find out in a few weeks” 🙄 I don’t want to wait a few weeks! Bad enough they originally gave me the 31st of December at first but I called and asked for something earlier because it’s the holidays and I didn’t want to wait that long so they only switched it to the 28th 🤦🏽‍♀️ big difference right ? Smh looking to change my doctor soon.