How come people have to use different citation styles, like MLA and more?
Why are there different citation styles?
I. Why so Many Citation Styles vs. Why Cite?
All of the tutors that responded to your question covered it and no reason to echo it. I do want to add that it is just as important to understand "why cite?". Ellie M. and Lauren gave one of the reasons which is "to avoid plagiarism". The other two reasons are because it gives credibility to the student's essays or term papers since it demonstrates to the instructor what he or she have learned in the topic that they explored and why they argued for their position. It is how ideas are tested to see if it is the case. The third reason is because researchers in their respective field conduct research which is than peer-reviewed by their colleagues which in turn promotes standard quality, credibility, and eventually be published in its respective journal.
Citation Styles. The University of Houston, 114 University Libraries, Houston, TX. 26 February 2013
As it has been stated we have to use citations to avoid plagiarism. However, each filed or area that one studies falls under a different classification and therefore a different formatting style. For instance, a paper in English would fall under MLA (Mondern Language Association) style. A paper in Psychology, Science, or even Social Work would fall under APA (American Psychological Association) style. Lawyers have their own style for citations. When you are looking at the subject you are writing for, be sure to comply the with the citation style that best fits the subject you are working within.
We have to use citation in our written and researched works in order to avoid plagiarism. Different citation styles are used in different scholarly works. It also depends on the preference of your teacher/professor. Here's a website that can help you learn about different forms of citations and help you understand the process further. http://owl.english.purdue.edu/owl/resource/560/01
There is really no reason why there are different citation styles (beside emphasizing the importance of one piece of information within the citation over another). Someone, somewhere in history decided he or she did not approve of one method for citing works and therefore developed another - in conjunction with a group of people who agreed (perhaps the creator(s) believed the other versions did not enable the human consulting the citations to adequately find a cited source). That said, everything else everyone else has said is also true.
While there are many citations styles, I prefer the one in the scientific community. Specially, the one most common seen in the IEEE and ACM Papers. This is the citation with numbers. Simple and to the point.
The study of ____ has been shown to be successful when using 3D Interfaces[4,6]. For more information, see [1-3]
You can also do (if more than three authors) In Brown et el., we can see....
or if is two, In Brown and Smith, we can see ....
To be honest, any other style is a waster of paper and ink. Also a waste of bytes, if you ask me. For example, say you only have 4 pages to express your idea, with graphs and formulas... do you want to spend time using MLA? or any other style that looks like MLA?
Also, if you are writing academic papers, use LATEX.