I'm also one of those people who notice the music more than the lyrics. I guess that's partly because I either can't always hear the lyrics or because they are too vague to know what they mean. But there are some songs where I really do appreciate them (like Don McLean, for instance). I always wished I could appreciate Bob Dylan the way my friends could, but I could never get past his awful voice.
Sometime lyrics seem to be abstract. For example, I have no idea what most of Yes's lyrics are about. Jon Anderson is surely a space cadet. But I think of the words as just a carrier for vocals. The vowels and consonants are put together with the music as if they were music themselves, even though they have no meaning. It's like an abstract painting. (I'm sure Anderson intends for his lyrics to mean something, I just have no idea what.)
I agree with F_cksia about why only songs with lyrics become hits. Not everyone can play an instrument, but everyone can sing and understand words.
One power, and perhaps danger, of marrying lyrics with music is that it often gives undue legitimacy to a message in the lyrics. You often hear people say something like "hey man, it's just like Twisted Aardvarks say in that song…blah…blah" and they go on to quote a lyric. But you're less likely to hear anyone quote famous poets that way. I forget who said it, but there is an often-quoted line about not using music for messages: "If you got a message, use Western Union".
Jim