Easiest solution is not to put them in?
Obviosly, but doing nothings always the easiest thing.
Also you don't need coins from evrey era because since the second era i think they've used septims.
So all they needed to add were Dwemer coins, and mabe Nordic coins.
Not that it's a big thing just a little detail i wish was in there.
Well I'd agree there is a practical problem. For instance not all Draugr invested ruins are from early ages, so you wouldn't have enough about one type of ancient nord coin, you would need a dozen different kinds. This is going to be a lot of work, I wouldn't mind if it were in there, but I think Bethesda has more important things to worry about.
I'm sure a modder could add them to the game in 5 mins
there is a mod for this already, but it has the problem I listed above. All Nord coins come from the same era, so it still isn't perfect.