How come Kakashi didn't teach Sasuke the rasengan?

[shelke]

Sasuke would have completed the Rasengan easily with his level of Chakra Control. But, it was the mangaka's decision to keep their styles divided to create distinction.

 

[lndra]

Because Kakashi believed that Rasengan was useful if he could apply Raiton manipulation. Because he couldn't, he sticked to Raikiri/Chidori, so in his mind, teaching Sasuke Chidori is more effective. Also, keep in mind that it takes many, many years for one to learn elemental recomposition and apply it to Rasengan which already requires a maximum amount of shape manipulation. Time was likely a huge constraint and by trying to teach Sasuke a Lightning Rasengan would not have maximized their training time.

Kakashi didn't even consider this for Naruto until Kakashi suddenly stumbled upon a specific training method which was only suited for Naruto. He likely didn't have a training method that could help Sasuke achieve it in a short period of time.

Perfect answer

 

[leezagboola]

We never saw Kakashi use the rasengan in Part 1 so maybe he hadnt even mastered it himself compared to chidori which was his signature.
Sides if Sasuke already had chidori which was a direct one shot attack, why bother to teach him another similar one shot attack move? It would make more sense to teach him another type of attack or defensive jutsu or maybe some genjutsu or taijutsu, not a similar one. That wouldnt really expand his arsenal it would just mean we would have a few panels of Sasuke using the rasengan and opting to use the chidori as he has the lightning affinity.

 

[Uzumaki Death god]

cause he didn't want him to waste his efforts on a jutsu he could never truly master