In my opinion it's because 1) generally speaking, politics is not considered a good topic on HN, 2) people often bring up the Palestinian-Israeli conflict even

In my opinion it's because 1) generally speaking, politics is not considered a good topic on HN, 2) people often bring up the Palestinian-Israeli conflict even when it has little or no relevance to the article in question, 3) it usually comes with an anti-Israeli slant, and often descends to comparisons with the South African apartheid, Nazi Germany, North Korea, etc. In short, it's rarely relevant and it easily leads to flamewars. Imagine that every time we had a story about a startup located in the US, someone would mention the large number of black people the US imprisons every year. Or the number of civilian casualties in the Iraq war, which dwarves the total number of casualties in the whole history of Palestinian-Israeli conflict.