Because people want to see Hayasaka happy. The person Hayasaka seems to respect and like the most so far is the President, it seems kind of unfair that she never really got to shoot her shot with him because she's so loyal to Kaguya. There's also a lot of similarities between their personalities. They both work extremely hard and take notice of other people's workloads (Meanwhile Kaguya runs on pure talent - she only really takes notice of Shirogane because his hard work challenges her entire world view). Hayasaka instead realizes right away what kind of man Shirogane is.

They also both put on a face that people think they want to see because they are insecure about their station in life. It's a bit sad in a way - Shirogane is rewarded for putting on that face long enough to get close to Kaguya while Hayasaka is largely left where she started...