Out of universe, I have not seen any concrete evidence that what I am about to say is correct, but...
The reason is Merchandising
This article explains a lot about the toy industry and what StarWars did to it in the beginning, however J.J Abrams did say this,
Yet even when the toys seem to supersede the films, the people behind
the scenes still hold true to Lucas’ original sentiment. The story
“What’s been incredible for me has been the creative freedom and the
desire to make something hopefully worth people’s time – and not a
commercial for toys,” J.J. Abrams told Rolling Stone. “I’m not itching
to be involved in creating things that end up in a landfill. I wanted
to tell a story.”
But, still, Disney did not buy the franchise to lose money.
Why Buying Star Wars and LucasFilm Is the Best $4 Billon Disney Ever Spent
Star Wars is a merchandise monster
While I'm sure Disney has sold a
lot of products tied into the Avengers universe, the numbers can't
approach the retail phenomenon that is Star Wars. Disney has smartly
tapped into the nostalgia many parents likely feel when it comes to
Lucas' universe. It made buying new Star Wars toys an event, which
kicked off Sept. 4, dubbed Force Friday, when it launch the first
batch of Force Awakens merchandise.
"That day alone Star Wars merchandise sales are estimated to have
neared $1 billion," The Atlantic reported in late November. Overall,
Star Wars merchandise sales could reach a potential $5 billion in the
first year after the release of The Force Awakens, which could result
in $500 million in licensing and retail revenue for Disney, according
to Macquarie Securities analyst Tim Nollen as quoted in that article.
And those predictions were made before the film was on its way to
being the biggest movie ever.
Again I have no concrete evidence of this ,but this is also why I think they made small changes to millennium falcon, see below, they changed the round radar to a square one. Changing just little things like this on any of the original characters or sell-able items in the movie, will inspire collectors and new consumers alike to buy again, even if they have the original version.
So I will leave you with a parting video that needs to be watched.