Ultimately, every system will break down somewhere. The SE system is not faultless, and one of the faults is that easy questions and answers get easy points.
SE has tried to eliminate some of that by firstly allowing answers to be marked as duplicates, secondly by giving equal opportunities to high-rep and low-rep users, and thirdly, by the fact of being a community, that is, not a whole lot of independent individuals, but a group of accountable users, each one accountable to the moderators and one another.
As I said, however, every system breaks down at some point. In the SE system, unless you can show that the answer is definitely a duplicate of a previous question, it stays there. Is this a default? Yes. Will people make use of it? Yes. But at some point, you have to ask where else you would draw the line. Should we be able to close this question because it is similar to other questions? Should we be able to close it because the information is elsewhere on the web? How hard should a person have to search both on AU and elsewhere before posting AU? These are questions that the moderators struggle with.
I haven't succeeded in finding an exact duplicate of this particular question. Hence, in the SE system as it stands presently, we cannot simply close it on the pretence that it would be easy enough to find the information elsewhere.
The goal of AU is to provide good questions and answers. When questions like the one you referred to are asked, while it does give an individual user a reputation boost, it does serve the greater good of the site by providing more answers, giving a greater search engine awareness, and consequently drawing in more users to produce good questions and answers.