Well I was going to say my I am and my DH is, then I read mencken's post
We are neither stupid, ignorant or mentally ill (FFS), we were just both brought up like that and it's stayed with us.
I see some of it as common sense though as well as superstitious, open umbrellas in the house are wrong because you'll get water everywhere when you close them, if you don't walk under a ladder you're less likely to get a paint pot on your head and if you don't cross on the stairs you're less likely to trip.
Some of it is fear of "jinxing" myself, it may be irrational (rather than ignorant) but show me someone who doesn't have a single irrational trait and I'll show you a liar
For this reason I wouldn't, for example, assemble a new cot before a DC arrives (again there may be reasons why this may be "sensible" in someone's mind and it would actually be ignorant to chastise someone for this IMO!)
Some of it is due to luck and simply hoping for good things, like putting a coin in a new purse before you give it to someone. It doesn't harm anyone.
I have to say I don't understand the new shoes on the table thing, or not giving gloves as a present or quite a lot more
I was taught as a child, but some are almost just a reflex now, the same way we are taught (for example) etiquette, automatically putting your cutlery at 25 past 5.
My DC sometimes eye roll at me the way I used to eye roll at my parents at their age, but I think they will grow up and, like I do with my mum now, think fondly of me when they're avoiding each other on the stairs 