There actually are scabbards that make drawing the sword from the back easy, to say that it was never done is probably a stretch too.
I mean if you want to start talking about these things then our characters wouldn't be walking around all day with big two-handed swords, big shields or wear armor all day.
Anyone who knows anything about armor knows how stupid the idea of wearing armor to the extent that people in video games do would be.
In regards to '' immersion '' if you want to take it this far then there are just a lot more major issues lol.

With that said I wouldn't mind it as an option so that you could choose.
For characters with shields and a single weapon I'd actually like them to wear it at the hip too.
I think that it might be easier to avoid clipping if you just fasten it to the back tho and also since we're seeing the character from top down it just makes it easier to see what you're carrying.
It's just one of these things in video games, like the whole huge weapons and shoulderpads etc.
People say the same in games like LoL, but it's a matter of function in game design.
It's not because game developers aren't educated on this and don't know any better.
In SFV for example they made the feet and hands huge to make it easier for your eyes to register quickly where things are, it's the same in RTS or MOBA's like LoL too the silhouettes are big and expressive because it becomes very hard for your eyes to register what's going on if things are more '' realistic ''.


In a singleplayer RPG this is less of a concern since it's not a PvP game.
But I still do think that it's a concern, things very easily start blending into the environment.
I know that people don't like hearing this and I think that often times it's wrong, but I think it's a little bit the matter of people not knowing what they want.
Something might sound better on paper but in practice it isn't.
It's actually a huge concern in WC3 Reforged, that they made the silhouettes too small and detailed and it turned the game into a clusterfuck that is hard to follow and on the competitive side it's a major issue and complaint.
But there were definitely a very vocal group of people who wanted a '' realistic '' WC3 remake.
But then when it actually came out suddenly people realized how bad it was.

Like I said I don't think that it's as big of a concern here in terms of balance, but I still think that it's an understandable gameplay design choice that ultimately is a part of a whole that comes together to make the game feel more responsive and easy to follow.
Both in terms of your own character and the enemy.