I think yardstick issues are common.
I would definitely agree with that. I share both your issues, my DH is 6'7", so 6' seems "quite short" to me and I have deeply offended people by saying that outloud at times. And amongst the children of a whole bunch of like minded professional types our kids don't stand out THAT much. In fact the ways in which they stand out most is probably sleeping less, being more intense, hard to keep up with in general, than overt "smarts".
and I do think this comes into it for our kids too:
I do agree with the previous posts that talked about personality being a factor, but I also think there is a parental factor involved as well. I am more philosophical than academic and dh is more creative than academic and so to a certain extent dd reflects what she is exposed to at home. The couple of stereotypically PG kids I have met have very academic parents who know and talk about academic concepts and theories as part of their daily life. Where as we tend to talk about life and people in a way that is possibly unusual. Neither of which I think is more valuable than the other, just different.
It's not intentional but I think that comparatively to some families we have radically under supported any academic pursuits in our children while they are small. They get endless support to play and interact but not much to read, write, etc. Just thinking about my 14 month old, she requires constant attention and stimulation. Since she was only a few weeks old she has been utterly miserable if not kept constantly busy. But as avid a reader as I am, and as much as my older children love books, it has never occurred to me to read to her until last week. If she needs stimulation I take her for an outing, put her on the swing, build blocks, do puzzles, stacking cups, shape sorting, etc. We are a reading household, but due to a particular set of circumstances reading to her just hasn't been part of how I've parented her - so she's pretty damn unlikely to start reading any time soon!
Then again she's shape sorted younger than her siblings and she's quite interested in books now that we are reading to her.
Edited to add: I have wandering around for hours pondering this and finally had a "Duh!" moment. We didn't start reading to her young because she screamed pretty much non stop for the first 4 months and I just don't think to read to someone who is screaming at me... After that things were still pretty precarious for the rest of the first year.