Scans before 12 weeks are not required unless you experience things like bleeding, have had prior m/c's or you need a dating scan. Increasing numbers of women seem to be getting them done though for to have a look at baby or to reassure them that it's really there, or that all is OK.

I had one at around 7 weeks with my last pregnancy but that was only because of spotting and my m/c history. If that hadn't happened the first would have been at 12 weeks.

I probably wouldn't have had the 12 week scan and BT if I was under 35 but many women do now. It only gives you a risk factor for the trisomies not a result so if you wouldn't have had a CVS or amnio then there wouldn't have been a lot of point to getting it done (other than seeing your baby I guess). Like you said they will normally pick up problems with the morphology scan later on.

I think doctors prefer to have found risky pregnancies earlier on though because if termination is decided upon it's better to do it earlier on as there's less chance you've felt movement by then which can make the decision a lot harder. I had already felt a movement when I had my amnio at 16 weeks but luckily all was well.

I wouldn't worry too much about it. People are always going to give you their opinions during pregnancy (and it gets worse the further you get along). More than likely all will be well. Sometimes having scans can make you worry for no reason, so it could be a good thing to avoid them unless absolutely necessary.