As white, you have a certain opening advantage because you have the first move. One of the ways to use that is to force a very solid position no matter what black does (losing the advantage in the process).
As black, it's harder. White has the initiative, and if he wants to, he can make the game sharp against pretty much everything black does -- doubly so if black chooses the simple way out by playing the same thing against d4 and e4!
One other issue is that even though you play the same moves, there is really an essential difference between d4 & c4 by white, and d4 & e4. The Slav is not the Caro-Kann, the Pirc is not the King's Indian, and the French is not the QGD. You could choose those openings (playing e.g. 1...e6 and 2...d5 against everything), but you would still need to learn very different things depending on white's first move.
But so it goes, that is chess. 1.e4 is really not the same as 1.d4.
There are some white systems, KIA, Colle etc that works basicly regardless of what your opponents put out. Granted, they won't work well against everything, but they give you a base, and when your opponent put outs one an opening that rips through KIA, you can prepare for those openings separately, and through that minimise some of your opening study.
Is there any opening for black, that's as universal as the KIA and Colle (all of them, zukertort etc), but that's still reasonable sound? Now I know Colle and KIA isn't completely sound, but they aren't at the sodium opening level.