Because outside the Street fighter fandom i think Juri is pretty much a no-name. so by saying Shadow is Juri your pretty much saying Shadows a no-name.
Should have kept it at just dark counterpart. I know Shadow isn't really evil. But I also think Shadow is miles more recognizable than metal sonic to the general public.
I'm just not as sure as you are that Sakurai would chose "importance" over popularity when it comes to echo choices.
Like I said time and time again, Sakurai could literally throw Shadow in over Tails, and that'd be it. I would be extremely wrong and he would be thrown in the game. I wouldn't be losing any sleep over it, nor do I think I could predict what he will actually do. Only going off of things that have been observable so far.
Just all I'm saying is the common ideas that goes for Shadow's inclusion could literally be used for Tails. Unique Up-B, animations, taunts, etc.
But Tails does have the seniority, iconography, and amount of fans for him in order to get in, it may not be
as vocal and vast as Shadow's, but they are there. (Also Juri isn't really a no name in the realm of fighting games, she's quite popular. Now outside of that, definitely not. Same could probably be said about Shadow, if you're not familiar with platformers or the modern series itself, you could probably not know who he is. But I digress.)
And I mean we did get Simon as the actual fighter instead of Richter or Trevor Belmont, or even Alucard. Despite two out of three making an appearance. So it does seem that Sakurai leans on seniority and iconography rather than popularity.
But I already stated my points and made myself clear, I feel like I'm just repeating what I already spoke on.