Did you know that many of the words in the dictionary are variations of the same word? Why the redundancy?
Because dictionary publishers realized long ago that people have different research habits. We don`t all think alike. While two people may be looking for the same exact word, they may look for that word in different ways.
Well doing keyword research is no different. People search keyword phrases differently, although many of the keyword phrases they`re searching for mean exactly the same thing. They`re just worded differently.
Also, Internet marketing is ultra-competitive.Why not give yourself every possible advantage?
If you can obtain high rankings for relevant, less popular keyword phrases, why wouldn`t you go for it? Why not give your target audience every opportunity to find you?
I going to continue to give my target audience every opportunity to find my website.
Dale King
Actually, search engines may penalize sites that practice such SEO. So, not only do you risk viewers being unhappy, but getting banned from some search engine results. 
~Roland
Actually, search engines may penalize sites that practice such SEO. So, not only do you risk viewers being unhappy, but getting banned from some search engine results. 
And rightfully so. Anyone who practices illegal SEO tactics should be banned.
Dale King
Actually, search engines may penalize sites that practice such SEO. So, not only do you risk viewers being unhappy, but getting banned from some search engine results. 
~Roland
Sorry for the l-o-n-g quote, but I have no idea what your post has to do with anything I said or quoted others 
As for long tail, it is something that should be monitored from time to time to see if there is a niche market / key phrase that may be explored. Plus, for those sites that are in a highly competitive (search word) market it may actually be a viable approach to highly relevant traffic until the site becomes more established.
Long tail / short tail are not mutually exclusive either.
~Roland