I *may* have lost my crap on someone while I was PG and I stood in line to get something heavily caffinated, while wearing sunglasses indoors at night, to try to get through the migraine.
(I let them know in no uncertain terms that if they really *did* try to give me decaf, I would then still have a migraine, and since I wasn't keen ongoing back to the hospital again for the 3rd time in 3 weeks because of the nausea, I would have if I took the [doctor approved] vicoden, I needed caffinated beverages.--what did they think was worse for the baby, the mocha or the vicoden? give me my blankity-blank drink)
I think there's a degree of "well, this is what *I* suffered through, so you have to too" at play--not in a mean way as much as it's...just how it works.
I mean, it's like, to grab another sometimes controversial example, breastfeeding vs. feeding on a schedule. Imagine for a moment your'e my grand-mother-in law--and that you were told by the doctors to never give your child anything but formula, and to never feed the child between scheduled feedings--because doing so would put the child on the road to ruin.
So you go through literally hours, daily, of your child crying/screaming becasue that's what you're supposed to do.
Then your great-grandchild is born and you are told that of *course* we feed the child when the child is hungry, not on a schedule. And of *course* it will be breastmilk, that's what we're supposed to do, that's the 'right' way to do it.
The human psyche sometimes revolts pretty strongly at acknowleding it went through some sort of hell for no dingdangity reason. So instead of going "wow, that makes sense, I ws told wrong", it's human nature to want to double down and say "WHAT? No no no, you MUST schedule the formula. That's the way to do it"
(plenty of people learn to say "oh, yeah, we were wrong", but I have gotten a lot more understandingof people who struggle to deal w/ the fact that they put themselves and their loved ones through some sort of pointless hell).
I think that goes double with anything parenting/pregnancy/etc because what's 'right' vs wrong is so...fluid. And individual.