You don't have the bigger picture. In fact sometimes you don't even know that a person in another country (or why not, maybe in another university in the same city) did what you were trying to do, or already knows something you don't.
Not to mention the Feuds, aah the feuds. Like something showing up in IEEE but in ACM it's gone and forgotten (or the other way round)
I'm a CS grad student at Technion, and that's basically how my advisor has described our grad-school process.
Paper 1: your MSc thesis.
Papers 2 and 3: If related to paper 1, combine into your PhD thesis.
3 related papers on one broad topic => thesis, you're done.
http://matt.might.net/articles/phd-school-in-pictures/