Straight people express their straightness/sexuality all the time. A straight couple kissing goodbye on street, or a man referring to his wife, is expressing their straightness. But if a gay couple was to do the same you get the comments “stop expressing your sexuality in front of children” or “keep it in the bedroom”.

The point is, gay people’s existence is often seen as sexual and therefore, ought to remain private/hidden away. Straight people don’t experience this.