Given enough time, people forget. Besides, the people today need
   the fame. The people 50-60-70-100 years ago don't need the fame
   anymore. They're dead. So new people get the fame. I just roll
   my eyes a bit when I notice it. "Oh look, that's just a
   reworking [x]'s idea... oh wait, it's not even reworked, just
   reworded". "Oh look, someone dragged that old theory from the
   dustbin and stuck their name on it. Groan". To me, makes Science
   look bad when that happens. But, as most don't seem to notice or
   mind, I guess it's just how it goes. I notice though and I like
   point it out when I see it. They got their fame off of somebody
   else. I feel justified in pointing a finger and going, "Bah,
   thief". Maybe they didn't steal and just happened upon things
   the same way. I mean anybody who reads a lot is likely to
   accidentally pick up combinations of words or proofs or ideas
   and not _realize_ where they came from. Still, it's good to know
   sources. I enjoy tracing back sources.