This is an interest point, some might that sega has an interesting, inconstant train of logic that has gotten them into shit. Some might say thats true.
You don't remember sonic adventure 2.
Because his running and movement animation in that game are different.
And he has powers in that game. and a different attitude.
Which would require different animations for tuants, movement, and voice work.
Which... is another character.
They do, and has been noted, by the people making sonic boom, the comics, people who make sonic games who aren't sonic team. They go though a lot of renovations before the product comes out. Sega released those bad games, because they were proud of those decisions at the time, that's it.
They do care, they care alot, they make shitty video games regardless of them caring.