No Changing Hair Styles/Beards After the Start of the Game. Why BioWare?

I'd say gameplay is necessary in a game? I understand your point, but games have a limited budget and a very stringent schedule. BioWare cannot do anything and everything. They have priorities. They have a list of things going in and things being cut. It's the dirty, ugly business of how games are made and this feature you want is just never a huge priority.

Geralt would have to trim his beard on occasion and there were a few hairstyle options at barber shops, but I'd hardly call that substantial or game-changing. Mass Effect 1 didn't have any sort of character creator available in the game after creating your Shepard, so I'm not really sure what you are getting at. Horizon: Zero Dawn is not even an RPG and has a fixed protagonist you can't customize at all to my knowledge.

Perhaps you just skipped the codex in ME3, but there was plenty of love and labor put into that game. Considering BioWare had less than two years to develop and ship the game, it's honestly amazing what they were able to do in such a short amount of time, and I'm not even including the introduction of a multiplayer feature.

I guess my issue with your post is "the little details" is so subjective, broad, and ambiguous that it's too unwieldy to try and justify in a discussion. There might not be "little details" you like in these games, but I'm certain there are little details others like that you merely gloss over.

Mass Effect 1 was a great game, but the gameplay was absolutely horrific. I've never heard of a third person shooter where you can't even aim. Not to mention, there was no body part hit detection and the entire experience was just holding down a trigger and pointing at sponge enemies. I enjoyed some aspects of the RPG progression (although a war hero having to learn how to aim with a sniper was hilarious), but a lot of the gameplay in ME1 was unpolished and quite frankly a mess.

Mass Effect 2 took that gameplay and made it fun. Was a lot removed? Absolutely. Did BioWare have a lot of time to make the game? Not at all. They did the best they could with the limited time they had and ME2 and ME3 are respectable games. MEA is an attempt at taking that refined gameplay of ME2/ME3 and regaining some of the depth ME1 had.

Reasonable minds may differ, but I find this rather low priority compared to the other systems and features that absolutely should be in the game.

Everything you stated is great and fairly accurate.  I don't mean to disparage ME2 and 3 as much as you may think.  The combat did indeed get better as well as many of the missions themselves.  And the codex was amazing.  I'm not saying the devs didn't care about those games.  In my mind, I feel like because of EA, they were shaved down experiences in terms of the amount of freedom they provided the player.  I have no doubt a ton of love and care is going into ME:A and I realize there is a budget/time restraint.  Something as small as this mechanic that is already in the game shouldn't be a difficult task compared to everything else they've accomplished.  

Implementing it not too long after release is just something that would be completely fan service.  It's not going to bother me in the least bit if its not there, but I know many people in the community would like.  Hence the reason I am asking for it.  

If anyone is to blame for the "shaved down experience," it's honestly the fan base. Most of what was removed in ME1 was largely criticized by fans. From the cookie cutter and generic planets to explore, to the horrific controls of the Mako, the game was refined and focused to prioritize the main story and characters over everything else. The only thing I can accuse EA of doing wrong is the incredibly short development cycles they provided ME2 and ME3.

I think the bigger issue is exactly "how" you would implement the feature you are asking for. BioWare could do a really poor job and just tack it on somewhere, but that's generally not their policy. Everything requires effort and finesse, no matter how small and insignificant it may appear. There's always a chance BioWare could do another Black Emporium of sorts. Especially with how much longer their games are becoming, there's a least a justifiable reason for why players might want to change their looks hundreds of hours into the experience.

I really don't understand when people come in a thread like this and get all antsy saying "No! Such a feature would be an abomination! An abomination, I tell you!"

I mean, don't use it then?

A small quality of life addition to the game that helps players avoid the frustration of restarting the game over and over, seeing an unskippable cutscene over and over, tearing their own hair out and howling at the sky over and over... when those who don't care about the appearance of their character very much would never even have to see the feature if they didn't want, never mind use it.

It boggles the mind.