Fantasy land is a wonderful place. For example, you don't (usually) get exhausted, you are stronger than in reality, you can fling spells. You can fight without a helmet on, though in reality that would be a death sentence. You don't need to go to the toilet, and men don't need to worry about feeling uncomfortable because their pants squeeze stuff they shouldn't.
So tell me: what makes boobs so fundamentally different from all these other instances where suspending disbelief comes easy?
Many things you mention can be easily written off as gameplay mechanics that have hardly any bearing to how Thedas really is. So while you can switch helmet visibility off, the character at the moment won't be thinking "Hmmm, I shall wear my awesome invisible helmet!". For them, the helmet is still where it should, visible as it was.
Same with friendly fire - you can switch it on an off. Do you think characters in the game just shout "now, let's get rid of that pesky friendly fire!' and ZAP!, they don't have to worry about it anymore?
You also don't have to go (on-screen) to the toilet or sleep (and apparently days and nights in Thedas last forever and are individual to each zone, despite having the night-and-day cycle established in lore?) for one simple reason - DAI is not Sims.
Some 'real life' stuff has to be taken out of equation, because otherwise it would make game more tedious - possibly every single game in existence, no matter how realistic (even those taking place in our mundane reality) will have some of these things streamlined or trumped by more or less necessary game-play mechanics.
I think most players know that, hence they suspend disbelief for those elements.
So it's unfair to cite those and use them as an example of how unrealistic Thedas is - to establish that, you're going to have to read some lore or pay attention to character interactions. We do know that they sleep, bleed, ****** and get tired. We do know that most physics work the way similar to how they do in our world, unless they're affected by magic (in a way that it was stated or underlined). So if Iron Bull tells Cassandra that 'ornamental armor is crap', or she says the same thing to Vivienne, we can safely assume that they know what they're talking about, within the context of the world they happen to inhabit.
Which I would counter with "And I suppose Varric's chest hair kept him nice and toasty warn as well?" 
I'd like to point out that majority of at least higher level armors for Varric does have a sturdy chest-plate to hide his priceless chest hair from harm. Iron Bull's armor also keeps him mostly covered, and that's despite the fact that him fighting bare-chested is a cultural thing (even Dorian calls him out on it and claims that it's stupid).