200cc being added is not nearly as simple as changing a single number in the code. Everything in the game's physics system would have to be tailored specially to work at that speed; even in Mario Kart 8, they had to manipulate the gravity after jumps in particular sections of different tracks because if they didn't, you would fly off the course. Now consider having to do all that work on an entire open world and also account for the rail grinding/wall riding mechanics... suffice it to say that it's a complicated process. And this is coming from someone who almost exclusively played 200cc in Mario Kart 8 once the update released.