It may be that they also don't understand that privileges don't really cancel each other out. Just because Lily had looks privilege and Snape had blood privilege doesn't mean they sudden become re-equal. In the wizarding world ancestry and magical power seem to count for more in certain circles (e.g. Borgin is obviously a creepazoid but his pro-pureblood stance lets him keep in with rich purebloods who have lots of dark arts items to buy/trade/sell), so Lily was still at an overall disadvantage.