Why do newscasters talk in the tone that they do?

Question

for example, why do newscasters voices fluctuate between low and high constantly and without emotion?

Answer 1

Most likely they learn that in newscasting 101.

Answer 2

cause most of them will have to face lawsuits if they say the wrong thing or look the wrong way while telling a story, so if they maintain their serious look then they have nothing to worry about, it's the sad truth people in America will sue for any reason you give them to!

Answer 3

The fluctuating is called "inflection", and it's a common performance technique for actors and speakers to keep them from sounding too droning or monotone.  It helps keep people interested in what you're saying.  The emotionless part is that they are supposed to be objectively reporting the news, without giving the impression that they have a particular opinion about it.  They also try to imitate a very basic midwestern accent without regional influences...helps them appeal to the widest possible audience.