Ableton Link is designed to allow multiple musicians to jam together over a network by syncing the tempo of their projects wirelessly.
When multiple musicians are involved, starting playback without a one-bar count-in would leave them uncertain about when to begin.
The one-bar delay or count-in provides a clear cue, ensuring that all participants are prepared to start playing together in perfect sync.
Please think of the one-bar count in as if it were the drummer hitting their sticks together before the band start playing.
If you would like to disable the count in, please choose the "None" option under Ableton's count-in settings.