Why would you use fixed manual bidding for a line item instead of leaving it to automated algorithmic bidding?

Fixed manual bidding is appropriate when you have specific, high-value audiences you want to prioritize, even if it means potentially overpaying slightly compared to an algorithm. This allows you to guarantee impressions for critical segments. Automated bidding, while efficient, aims for optimal performance across broader goals and might not aggressively pursue every impression for a niche, high-value audience if it finds cheaper alternatives. The other options are less accurate: "Enough performance data" usually enables more effective automated bidding, not less. "Factoring in more variables than Bid Manager" is unlikely; algorithms often process vast datasets and complex signals. "To see if your intuition can beat the algorithm" is generally not a sound strategic reason for manual bidding; algorithms typically outperform human intuition over time for optimization tasks.