Remember back in the day when television networks attempted to show no limit Texas Hold’em tournaments and cash games without showing the player’s hole cards? The average spectator found it boring and it never took off.
Fast forward a few years later with the introduction of the “hole cam” and people were able to see what each player held and how they played each hand. The poker players at the table initially hated it but when the popularity of the game took off (partly because people were better equipped to understand how the game was played by the pros) and cash prizes for tournaments skyrocketed the complaining mysteriously ended.
TLDR: Allowing a spectator to see your build allows him to see how the build is played and arms him with more information which he can use while watching the match.
