I think the first example is just because people like to talk about themselves and their pregnancies.
I think the second example is because people feel like they need to make excuses as to why they didn't wear heels or look stylish (not that one needs to wear heels to look stylish) when they were pregnant.
The third, there's just no excuse. Why would someone say things like that to a pregnant woman? That's terrible!
Anyway I'm glad you're feeling great and having an easy pregnancy. With my first I wore heels up until the end too. The only reason I didn't with my second was because I was busy chasing a 2-year-old, so I wouldn't have been wearing heels anyway.
It's nice to be important, but it's more important to be nice.