all shows have the categories the issue is "best in show" at the very large shows where large amounts of money are won and careers are built once you win.
local guilds can do whatever they want and all they risk is a loss of a few members.
big shows have much more at stake - i'll never forget when the machine quilted piece won best in show for the first time - it was as if a person was actually hanging at the show instead of a quilt. women were actually yelling at the paducah staff right on the floor of the show.
not to long ago the 3 time winner of "best in show" at paducah was being beaten up on this forum over her work and the price of her quilts. she's the only person in the history of the show to have won best 3 times and she still doesn't have other quilters respect.