Off-hand, the easy out would be that 'giving people what they want' is actually pretty costly. The steep pilot culling selects for mass appeal. If 80% of the (paying) viewing public like a pilot, it's probably a low-risk venture with pretty predictable rewards. If those returns (ROI) are sufficient to keep the studio running, do the people writing the checks really care that more niche products _might_ gain slightly better rewards?