I absolutely consider thinking of things that are pure rule of cool/plot convenience as being more acceptable than an idea that has more basis in science fact for no real reason as being a double standard.
"These ridiculous technologies are fine, but this not that far out there technology isn't because reasons".
The hordes of mercenaries that get absolutely slaughtered.
I'm sorry, but throwing them up as an example of why armor is effective in this setting isn't a good argument. If you want to complain that Bioware is portraying catsuit wearing Miranda and topless Jack as more combat proficient than the legions of mooks wearing armor, complain about that, but don't call them idiots for not wearing armor when they're demonstrably more dangerous than 99% of the people who do.
Perhaps you've not noticed this discussion is about aesthetics, not actual gameplay mechanics. As near as I can tell, the mechanics haven't used actual armor values for Shepard & Co. since ME1. Starting with ME2, Shepard's armor choices gave other types of bonuses. And a lot of the enemy mooks who appear to be wearing armor don't actually have armor defense layers in their stats.
But since virtually all of the other non-monster mooks we face in the games appear to be wearing armor, that sets the overall visual aesthetic for MEU. Companions who don't wear armor look out of place in that setting, and there's your double standard - they don't follow the same rules that are applied to everyone else. They look like brainless twits who don't have the common sense to prepare for hazardous situations. I could argue that Jack would be the first in line for combat armor, since self-preservation is her priority one. A 700-year-old warrior monk would have protective armor, too.
When necessity, practicality, utility, and efficiency are the sole/primary concerns, everyone ends up looking homogenized and boring. Miranda, Jack, Thane, and Samara all have unique and interesting looks that help separate them from the pack and make the stand out. I do not care how impractical those outfits appear to anyone - none of us are the arbiters of what does and does not qualify as light armor in this series - I care that the characters have distinctive, memorable appearances.
Once that is established, then we can worry about practicality, as far as I'm concerned.
And I like equipping them for combat. It was a part of role-play I enjoyed in ME1, and have not been able to do since. I vaguely remember having a bit of trouble picking out Garrus in his ME2 blue armor on the battlefield, when most of the enemies were turian Blue Suns who looked just like him at a glance. ME1 allowed me to put the entire team in the same armor if I so desire - and I really miss the ability to make my squad look like a cohesive combat unit in combat.