Why is effective communication skills important?

I feel that communication is an indispensible tool wherever we go. As long as you have to work with people , you need the skill.For instance, I often have project assignments in school that required me to work with people whom I have not work with or even spoken to before.  Effective communication skill in this case is important. How can I phase my words in a way  that doesn't make me sound bossy when I am trying to assign the tasks to my group mates? Or when I disagree with my group mate's idea, how do I share my views without sounding insensitive but still unambiguously?  Communication is not just simply to say what we want to say. We need to be conscious of our tone and the words we  use  need to be sensitive and appropriate to the situation. This is always my concern as I often fear that I might be too direct and may make hurtful comments unintentionally. 

Another reason is that I feel that my presentation skill needs improvements. My area of weakness is my lack of confidence and poor interaction with the audience. During presentations , I often feel tense and worried that I will forget what I am suppose to say thus this affect the fluency of my speech. Furthermore, due to my nervousness, I wasn't  able to make my presentation more interactive and interesting to the audience.My presentation style is more of reading out loud about the information that I researched.  Hence, I hope that I can master the skill of having effective communication through the es2007s.