Well, if everyone in the world has it, it will probably be assumed as "normal" and people would tell you "not to worry about it, everyone has it and its normal". It's easier to just tell people something like that, than to be curious and find out why things are the way they are. People always tend to go for the easiest route. It might in fact even prevent/cancel any ongoing research because of this, as people just "live with it".
Tinnitus is unbelievably common already, if you have to believe the statistics. Folks from all walks of life are affected (from the rich and famous to the impoverished), yet this still doesn't change anything (apart from a few lost William Shatner videos with 25 views). I believe (a majority) of people without Tinnitus are needed, as counterweight, in order to come to the realisation Tinnitus is in fact NOT normal.
We are in the best position already. We are with a group large enough in order to make it interesting for companies to develop something, and small enough not to let Tinnitus be perceived as "something normal". Despite this, we are still waiting as there is hardly ANY awareness about this issue (which is hard to believe with such big numbers).
Point is; what you probably expect would happen if everyone has it (a faster cure), would not happen and perhaps it would even make a cure or treatment more unlikely.