Sense of Location Anyone?

So, this one is going to be one of the more angry rant pieces. You ready for the ride? (Clicks imaginary pen menacingly)
Have you ever noticed how sometimes in fiction, especially in television shows, people seem to sometimes talk very private things in not so private places while people are around? Like one guy student will be in the middle of a hall full of other students and yet confess how he's dating a closeted guy also from the school. Or two agents dicuss that they work for some secret organisation devoted to saving the world from secret aliens while walking down a main street. Or two culprits discuss their plans for dealing with a police investigation while in a ballroom. It just seems like it's easy enough to either move, or wait, rather than have a risk someone might, you know, OVERHEAR.
Now, I'm a pretty bloody honest person, but I do have some things I don't just tell. And some of those things I'm very careful with. I wouldn't just go blurting them out where someone might here. Not unless I slip up. Which is the issue, nobody regrets it, and nobody stops the other and says "hey, could we do this someplace else?" Not in the scenes I'm talking about. Other scenes do have the grace to do one of those and spare my keyboard from angry high-speed typing.
Which brings me to the question: why do writers write these scenes? It seems like they are doing it for no reason. Why didn't they just write the scene with the character have a better sense of location? It's not like it's harder. Just design the scene differently. You don't have to change anything as long as you don't set up the stupid version. ANYTHING but the stupid version!
It just screws with my suspension of disbelief, however much I'm suspending it, when I see this occur. I end up spending half the time reading/watching the scene thinking, why are you doing this HERE?
"Oh, I have this secret thing I want to talk about, let's do it where FIFTEEN OTHER PEOPLE COULD HEAR!!!!"
Does anyone know why this happens? Because it really pisses me off.
Maybe it's because they're hoping other conversation will distract people/drown out the sound? But that seems too risky to me, why bother taking that risk? Especially when it's with characters dealing with really serious secrets that affect hundreds/thousands/millions of people. Can't they just pick A BETTER SPOT?!!
I'm very picky about this stuff, I admit. I often think that they should be going for maximum possible realism. If it's a plot point, like magic, fine, but everything else why not just be realistic? I mean, my thoughts on writing are obviously superior, right? I'll never understand this weird race called "other people". Urgh.
But seriously, this one I struggle to forgive. Why??
Anyone got any thoughts on this they'd like to share?
Thank you for your time. Hope you have a good day.