Hamlet does in fact confront his mother, in Act III, Scene 4, and lambasts her for marrying Claudius, who is a pale reflection of his father. He expresses disgust at what he calls incest, accusing her of living in:
...the rank sweat of an enseamed bed,(100)
Stew'd in corruption, honeying and making love
Over the nasty sty!
She has betrayed his father's memory by marrying his uncle so quickly, a fact he makes clear even before he tells her that Claudius was guilty of the murder of King Hamlet.