Admittedly it's more obvious to us left-brain-dominant types, and especially to computer programmers (amongst others). Programming a computer is an act where you cannot afford to make assumptions or leave things out; there has to be a bit of code for each contingency, even the unusual ones and the ones that might never happen and the ones that seem like "special cases". In fact, those situations generally take up most of the effort when writing a program. You can't just be vague about what happens in those situations, but users who are describing how a system should work invariably focus on the "regular" course of events and get vague once you get into exceptions.
That's certainly not the only place where it matters to say what you actually mean, and mean what you actually say. I'm currently nearing the end of a huge, multi-year, very complicated, and very stress-inducing project at work, and largely due to the vendor, but also in part because of my own mistakes and things I didn't know well enough (but I know now!) the project has been quite badly managed. At any number of points throughout it, we've had large problems creep in on us precisely because someone didn't say what they actually meant, and settled for close enough. And invariably this turns a tiny little detail of trivial importance into a substantially larger problem that consumes a lot of time we can ill afford to fix it.
What's irritating about this is not the problems and having to solve them. It's that I have to defend the idea that precision matters. That taking two extra seconds to say the right thing now isn't just a good idea to save the two hours you'll spend at the last minute a month from now fixing the mess caused by ignoring the details and being vague, it's also a good idea for its own sake.
It really matters. Don't make me the bad guy for being the one to mention this fact. The fact was there even if no one had mentioned it.
To my readers, sorry to use the blog to vent a frustration. In a month or so, I will have a lot less frustration to vent.