nit picking

I had been to a college function in the village that I was living in last year and next to me sat a retired school teacher. The students presented the usual ppts and the first thing I noticed were the spelling and grammatical errors, but kept quiet. Just then the school-teacher next to me commented "It's a professional hazard; all one sees are the corrections" and she pointed out the same spelling errors. True, it's a professional hazard.
But is it? Perhaps those of us who like to do this kind of nit-picking take to teaching as a career. Like the chicken and egg, which way round is it?
I not only post on my blog, but every time I post, I check my previous post and make spelling and grammar corrections that I do not see when I type in a hurry.
I think those who teach do so because they like to nit-pick.