I have a question?!

I've been seeing a lot of posts where some ladies are being seen at 6w and others at 8-10w. When I called to see if I can move my apt to 6w instead of 9 weeks after leaving me on hold for 15 min. She said the dr. Said there wasn't really anything they could do for me at 6w, and I need to keep my apt at the 9 week Mark . unless I start bleeding then I can be seen earlier. Why can some go in at 6w to see the heartbeat and other Dr refuse to see you until 8-10w. Thanks in advance!