OK, this isn't really a scorer's decision, just a question about "why are the rules like that?" But maybe it's come up in discussions among your peers. When the defense commits an error, the inning is reconstructed by the scorer to determine earned runs. When there's defensive indifference, not so much. Last night Matt Belisle gave up a meaningless earned run in the ninth. With two out, a batter walked, who then took second on defensive indifference. A single scored him, and then the last batter struck out. If the inning had proceeded more normally, it's reasonable to assume the game would have ended with runners on first and third. No way that runner "earned" his run, so why should the pitcher have it hung on him? It's a matter of what the defense did, moreso than the pitching - why are the cases not treated similarly by rule?