Thats the way the Lucas SW6 played out,....he had influence from 'The Hidden Fortress' directed by Akira Kurosawa, in which the story is told from the perspective of two peasants, after squarrelling & splitting up they end up getting captured, reunite & get caught up in the story.
R2 & 3PO are the constant throughout Lucas's Star Wars films, R2 continuously steps in to save our heroes or undergoes secret missions
The new Disney films either don't understand this, or have purposefully decided to change this perspective
There are many who feel that Han, Leia & Luke's characters have been mis-handled, but poor R2 has been left out of this trilogy
Its very strange that theres a build your own R2 or BB8 at Galaxy's Edge
J