Depends really.
Hardcore don't exactly need lyrics, as its mostly just the tune you're listening to and dancing to...however if it has some good pumping lyrics getting you to go harder and faster, thats also a plus...
Then you have things like Happy hardcore, with the cheesy lyrics...that are needed, otherwise it wouldn't BE happy hardcore.
On non-electronic music, i think lyrics are essential, they need atleast SOME type of meaning behind them, even if its little or small.
But with that being said, they also need to blend with the music and "go" with the tunes behind it.
Personaly, i dont mind having lyrics not mean anything, but if they do? its an added bonus.