How often do people ask? Seriously. I have seen a few folks ask on here, mostly laying out their expectations about one thing or another and then asking if their expectations are realistic...
but IRL ("in real life" for those asking about abbreviations), the folks I know who are pregnant (and sometimes the folks who are TTC) are already getting a ton of unsolicited advice and don't feel the need to collect more opinions. I've noticed that the majority of parents-to-be also have tons of their own opinions about things, and are already sure that things will go this-way-or-that-way if they do this-thing-or-that-thing.
I think that's the biggest thing that parents-to-be do that is unrealistic. They'll acknowledge that perfect parenting, etc. isn't possible, but then they'll go on and list a bunch of things that they are going to do with their kid. And that's not a bad thing...it's good to have thought things through. But the biggest reality check that happens is when you can't do everything you set out to do with your kid, or be the exact parent you set out to be, and then--and only then--are you able to really process what that is like and the grief, guilt, or feelings of failure that sometimes comes with it. Of course on the flip side, there is also the elation of finding what is positive but unexpected.
I just don't hear ttcers and pregnant folks asking all that much. I mean, I have a friend who asked me a lot of specific questions while pregnant, but I think for her she wasn't asking for a "reality check" as much as for very specific advice on particular preparations. If I would have taken that opportunity to dose her up with reality checks, I think she would have stopped asking.
I don't think you can rush the process of transitioning into the realities of parenthood. Everyone is going to have their own process, and folks aren't usually able to fully *hear* certain things at certain points in the process. I try to be honest about the specific things people ask about, and also helpful in terms of specific advice. When ttcers and pregnant folks are talking about their various expectations, I never "correct." That's part of the process. I nod, smile, and provide a listening ear, and every now-and-then throw in a story of my own parenthood or two for balance but not as a direct contrast to what they are saying.
And then I wait for the day to come when they are "in the trenches" and need my support, which often times is in matters unexpected/unanticipated by me.
I'm pro-adoption reform, but not anti-adoption.