Because it's stupid to go to a huge amount of effort to figure out your exact unit cost to reduce prices to when customers are prepared to pay more, and cost st

Because it's stupid to go to a huge amount of effort to figure out your exact unit cost to reduce prices to when customers are prepared to pay more, and cost structure usually isn't linear enough to make this practical anyway. It's like asking "why shouldn't workers work for subsistence income instead of asking for more money?": the obvious answer is "because the only reason they would consider doing so when they don't have a choice"