Like everything else in the current electoral system - superdelegates, closed primaries, etc etc. - the process is preserved to cement the current power structure. If you saw the way the RNC roll call vote went down, Reince Priebus called for the "Yea"s, then gaveled the vote as a YEA before even hearing the "NAY"s. It's to ensure a completely subjective voting experience which can be obfuscated to the party's advantage.

Like why so many of these violent unjustified police encounters start with "the officer detected an odor of marijuana coming from the car." It's something subjective they can write on the report afterwards since how can you argue with someone's sense of smell? (Or the volume of a room full of people screaming YAAAAAAAYNOOOOO!!!)