Do you think that a lot of people would have gone and see TrekXI in the cinema's if they were completely new characters?
They might have. Star Trek
alone is a big brand name. But it would have been more of a risk. Just think about the position JJ Abrams was in - if his movie had been a flop, it could have been a total catastrophe for the franchise, "proof" that nobody wants more Star Trek
of any kind.
He was under a huge amount of pressure to just succeed
. He crafted a movie that was both respectful of existing canon and geared to make maximum box office among the majority of the audience who think "canon" has something to do with the Catholic Church.