I don't know about a seriously comprehensive study, but there's data to show it was significantly harder to win away from home, which implies it's significantly harder to get the goals that result in wins away from home. But it's declining and I think home advantage is overrated (we've just seen Spurs and United get hit at home when they were supposed to be in "advantageous positions").
Home advantages also means a fuckton of nerves, real fear of conceding those away goals, getting stuck somewhere between attack and defense, not getting much value out of grabbing home goals relative to what you'd lose by risking conceding while trying to get those away goals. I'm not convinced, I prefer my team to be away from home in the second leg where they can adjust their tempo to get killer away goals. And so that means I agree with you, those away goals are treated too valuable.
But it's part of the sport and sets up a lot of drama. Without aggregate wins you can't go from progressing to getting knocked out in the space of a single goal so you can't get dramatic last gasp wins.