Why doesn't Calpurnia want Caesar to go to the Capitol?

Calpurnia, Caesar's wife appears only once in the play in Act II Sc.2. She is presented as a very troubled and anxious lady deeply concerned about the safety of her husband. She pleads with Caesar not to go to the Senate because there have been reports of very bizarre happenings in Rome and she herself has had  a terrible dream. Just then Decius arrives to accompany him to the Senate, and Caesar narrates to him Calpurnia's dream and tells him that he won't be coming to the senate:

"Calpurnia here, my wife, stays me at home; 
She dreamt tonight she saw my statue,
Which like a fountain with an hundred spouts,
Did run pure blood, and many lusty Romans
Came smiling and did bathe their hands in it.
And these does she apply for warnings and portents
And evils imminent, and on her knee 
Hath begg'd that I will stay at home today."

Calpurnia foresaw in her dream the assasination of Julius Caesar. She saw in her dream the statue of Julius Caesar being transformed into a fountain from which spouted not water, but blood and the Roman citizens smilingly washing their hands in his blood.

Inspite of Calpurnia's brief appearance, her role and character are important because:

1. To contrast the private, domestic life of Caesar with his public political life: Caesar makes his first appearance on the stage in a "nightdress" and the very first lines that Caesar utters refer to his wife, "Thrice hath Calpurnia in her sleep cried out/'Help ho! they murder Caesar." From the beginning of the play till now all that we have heard about Caesar relates to his warrior like and statesman like qualities. But, Shakespeare foregrounds his first appearance on the stage by presenting him as a worried and anxious husband who is ready to please her initially by agreeing not to go to the Senate,"and for thy humour I will stay at home."

2.To contrast fate and human will: Calpurnia's  intuitive fears,"O Caesar these things are beyond all use/And I do fear them,"  are contrasted with Caesar's self confidence, "It seems to me  most strange that men should fear/Seeing that death a necessary end/Will come when it will come."

3. Calpurnia's  interpretation of her dream is brushed aside and Decius' interpretaion is accepted by Caesar to emphasise the significance of the public and the political over the private and the domestic, "How foolish do your fears seem now, Calpurnia."

4. Calpurnia represents the fear and the superstitious beliefs of the  contemporary Elizabethan audience concerning the supernatural.