Yeah. To get an aggregate draw if you lose away from home you need to win at home, which is also going to send you through every single time if you draw the first game anyway. I don't get the difficulty in understanding that.
And in a scenario where you 'win' the second leg in 90 minutes to reverse the scoreline to reach an aggregate draw, you still have to get through extra time and penalties where as if you win by any margin in the second leg, you qualify. Silly opinion really.
To break it down simply:
If first leg: Madrid 2 United 1
Second leg scenario:
Madrid score 0, we have to score 1 to qualify
Madrid score 1, we have to score 2 to reach extra time
Madrid score 2, we have to score 4 to qualify
If first leg Madrid 0-0 United
Madrid score 0, we have to score 0 to reach extra time or 1 to qualify
Madrid score 1, we have to score 2 to win
Madrid score 2, we have to score 3 to win
So how is any defeat (even with away goals) better than a 0-0?