From my experience, friends who haven't had the 12 scan have done so because they will keep the baby no matter what. For me, I have it because to date I haven't been offered a scan beforehand so it was the first real chance for me to see I was pregnant (I dont have blood test to confirm either). It's your choice and I find it odd that people feel they should judge you on that. But everyone seems to have an opinion about everything in pregnancy (usually from people who are not pregnant)!
I do have a family member who was advised NOT to have the 12 week because she was 23 and had a healthy bub, but unfortunately at the 18 week they discovered severe brain damage and the baby died at 38 weeks (would've killed the mother to birth him they later found out). I find that totally neglegent as it wasnt' her choice not to have the 12 week but the Dr's choice. She would've aborted early on too.
Stick to your guns and don't let others questioning deter you xo