At least, that's my opinion. Consider this:
ROB is a joke character. If anyone has seen gameplay videos of him, he appears to have a very limited range of motion, meaning very simple moves and animations. Therefore, he would take a very short amount of time to implement in the game. In addition, R.O.B.s are already SSE enemies. That means that they already have models, limited moves, and limited animations. They are partially implemented already, so it wouldn't take too much time and effort to implement him as a fully playable character, compared to the effort required for a brand new character, or even a partial clone. Therefore, it is my belief that the development team put a little extra effort into making R.O.B. a playable character, but this "little extra effort" would not be enough to implement any new character, so he didn't take anyone's spot on the roster.
I may be right about this, and I may be wrong, but thinking about it this way makes R.O.B.'s inclusion much more tolerable for me.
ROB is a joke character. If anyone has seen gameplay videos of him, he appears to have a very limited range of motion, meaning very simple moves and animations. Therefore, he would take a very short amount of time to implement in the game. In addition, R.O.B.s are already SSE enemies. That means that they already have models, limited moves, and limited animations. They are partially implemented already, so it wouldn't take too much time and effort to implement him as a fully playable character, compared to the effort required for a brand new character, or even a partial clone. Therefore, it is my belief that the development team put a little extra effort into making R.O.B. a playable character, but this "little extra effort" would not be enough to implement any new character, so he didn't take anyone's spot on the roster.
I may be right about this, and I may be wrong, but thinking about it this way makes R.O.B.'s inclusion much more tolerable for me.
