Looking at
http://dnd5e.wikidot.com/sorcerer:wild-magic, the wild surge table doesn't have anything that's super hard to implement. Switch couple with something else inventive and should be relatively simple, just takes some work.
Nothing super hard, but there's a load of special cases, some modelling and animation and an interface for the whole system including possibly rerolling if the game gets to level 14. They could probably implement an extra subclass for every class, three more subclasses for Sorceror and two new races in the time it would take to implement that table in its entirety. It would make far more sense to adjust every part of the table that doesn't generate an effect produced elsewhere. Or add an alternative subclass that's easier to implement and likely to be more popular.
I am not so sure, if the table would require so much work. Apart from certain spells, e.g. Fireball, most stuff is already in the game.
Sure, something like "You can't speak for the next minute. Whenever you try, pink bubbles float out of your mouth" needs extra work, and if they deem that as to much work, it will not hurt much, if the change it a little bit for something similar, e.g. you grow a pink beard (that is something that would already be in the game).
