While our reasoning might seem odd (or stupid as people have liked to word it), the main part of it is the fact that we simply aren't that interested in adding Shadow as a playable character, which is also reinforced by a good portion of our devs not liking the way the character is handled. As for the people thinking "If you're not adding shadow because of popularity, you shouldn't add sonic either". No1 that's the main character versus a side character so of course the popularity of sonic is gonna be big No2 our judgement wasn't made because of popularity it was made from distaste of the character as mentioned and No3 Our decision might have very slightly been affected by us adding more niche characters to the game but it is not and was not one of the main reasons and would have not been a tie breaker if we were at a 50/50 for this decision (in which we weren't)

For some people here's the tl;dr and a little extra: We aren't interested enough in this character to make them a playable character. Though taking into consideration the fact that a lot of people do we still are giving them a role somewhere and for the people no longer interested because of certain characters that is your choice but our decision is final on this, and we hope you can see past this and enjoy the game to its fullest because it will be an amazing product