What you call 'screaming' is very much singing. Bands use vocals that sound 'pleasant' to make up for the lack of pleasantness in the music itself. While this so called 'screaming' is an artform in a different style. They don't need to get people hooked on the pleasant vocals to get them to listen to their music, the instruments are good enough so that they can do a different approach.

Too much music these days are too vocal oriented. If you was to take the vocals off most songs all you would here is a simple chord progression repeating itself over and over again. The song would be pathetic as it is... But on most metal, you could remove the vocals and still enjoy the song. I personally hate music that is oriented around the vocals. They have a couple verses and they repeat the chorus over and over and over again. While the instrument work is very very dull. In most cases vocals are an easy plot to draw your attention away from the 'lacking' instruments.

Screaming isn't that easy too.. I've been working at it for about 3 years now and still can't do it for more than a minute without choking on a lung.

I'm not trying to argue with you are start any kind of argument.. Everybodies opinions are their own.
It's just when I see somebody say they don't like a certain kind of music mosty because of the vocals I feel they are totally missing out. And it automatically turns on my 'defense mechanism'. hehe

okay, everybody got his own taste,but for me,the music and the vocals got to be in harmony with each other,because it just sounds better to me.

If you want to hear some of the best metal their is with non-screaming vocalist check out Nightwish. They have a female vocalist that sings in kind of an opera style. It took me a while to get use to the change from the type of stuff I usually listen to but the music itself is so good I couldn't just not listen to it. Now I listen to that band every day. This band's music is the work of real artists. It's not your mindless shredding type metal.