Depending on your proportions, some necklines might work better for movement or fit. Like, high necklines on a rectangular t-shirt, if you're well-endowed, have a tendency to creep up and get all chokey. Scoop necks do a better job of this.
Some people might consider scoop neck to be "low cut" (because the collar bones are visible--something generally not accepted/expected of men) while others might not call something "low cut" til cleavage is visible.
Now, a button-up shirt does a nice job of leaving space for your throat so you don't feel like you're choking, but in case you haven't noticed, it can be difficult these days to find button-up shirts for women that have all the buttons. It has become extremely common to manufacture women's blouses without the second button, or rather, with the second button roughly 6 inches below the first one. I suspect this is due to rules in schools and workplaces allowing for the top button to be left unbuttoned. That way, you're following the rule and showing some decolletage. I once went through every button-up blouse I could find at Target. I came away with having found one rack that had shirts with an upper-chest button. (Oh, and if you button all the buttons on one that's missing that upper-chest one, it just gapes open)
If the shirt itself is not quite wide enough to accommodate being well-endowed, a lower neckline can allow the fabric to move horizontally to better fit around the girth involved by opening up a bit wider. On the one hand, you could get a bigger size (if that's even available--there are limits), but if you've got a small waist, there's a tailoring problem for you. And if you've got shoulders that are narrow but a chest that isn't, that's a much more difficult tailoring problem.
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Re: bar. I'd rather be asked "read any good books lately?" than told "that dress makes your boobs look good." But then I'm someone commenting on Hacker News, so that might be to be expected.
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Re: your wife. I suspect there's a standing agreement with her regarding how you interact in terms of expressing your sexuality. I doubt you'd comment to a male coworker on how his trousers make his lower half look, but if you were married to a man, you might to him.