Naruto question, If Naruto is not the reincarnation of Asura (Sasuke/Indra) than why do they look so similar?

I'm not sure I really see a resemblance, besides the short spikey hair which isn't a unique style.  In life Asura was brown haired and dark eyed, nothing like Naruto who very clearly resembles his own parents.  Same with Sasuke who's nothing like Indra. The reincarnation of Asura and Indra is a chakra and spirit based one.  Naruto and Sasuke are both the reborns, but only inherited their chakra and traits of their will and intentions.  

Physical looks are still genetic to their parents.  Hashirama was the previous incarnation and he looks nothing like Asura or Naruto.  They're still their own unique people otherwise.  Naruto is more like an echo of Asura, not Asura directly himself.