The Lucasfilm Story Group has literally billions of dollars riding of decisions they make.
Probably the two story elements fans have been eagerly speculating on since The Force Awakens have been
Who are Rey's parents?
Who is Snoke?
Yet we have a pattern in The Last Jedi that these questions
were not addressed or were resolved with a potentially surprising non-answer,
Nothing about who Snoke is or his origin, and that Rey's parents are "nobodies".
Clearly a lot of thought went into this by the key members of the Lucasfilm Story Group, Rian Johnson and probably J.J. Abrams.
I could speculate that some of the thinking may have been that:
It was too difficult to resolve these elements differently without creating too many plot holes in previous material. Or that it was deemed too risky that any more specific resolutions (Darth Plagueis, Mace Windu, Jar Jar Binks; Luke, Obi Wan, Palpatine) would alienate too many fans and create too much backlash.