Why were Calpurnia and Portia disregarded in Julius Caesar?
Brutus's wife Portia was not disregarded. She was not trying to prevent Brutus from doing anything; she simply wanted to know what was happening. It was obvious to Portia that Brutus was involved in a very serious enterprise with a group of other Romans. In Act II, Scene 1, Portia finally wears Brutus down and he promises to tell her everything she wants to know.
O ye gods,
Render me worthy of this noble wife!
Hark, hark, one knocks. Portia, go in awhile,
And by and by thy bosom shall partake
The secrets of my heart.
All my engagements I will construe to thee,
All the charactery of my sad brows.
Leave me with haste.
Shakespeare does not ever actually show Brutus confide in his wife. That would be redundant because the audience already knows everything about the plot to assassinate Caesar. Instead, in Act II, Scene 4, the audience realizes Portia had her wish and is now terribly upset and worried about her husband. Brutus kept Portia in the dark because he wanted to spare her the kinds of emotions she experiences in this scene. She does not express any wish to prevent her husband from conspiring to kill Caesar. Brutus is already at the Capitol with Julius Caesar, and Portia now knows an assassination plot of historic proportions is about to be enacted. She wants the plot to be successful because her own fate is tied up with her husband's. She has become an accessory before the assassination even happens. Through her own curiosity, Portia becomes a co-conspirator. She doesn't know how to act in such a role. She is afraid of giving her guilty knowledge away to the servant Lucius. Her last words in the scene are,
I must go in. Ay me, how weak a thing
The heart of woman is! O Brutus,
The heavens speed thee in thine enterprise!
Sure, the boy heard me. Brutus hath a suit
That Caesar will not grant. O, I grow faint.
Run, Lucius, and commend me to my lord;
Say I am merry. Come to me again,
And bring me word what he doth say to thee.
Calpurnia, on the other hand, is not curious about her husband's affairs because they are public knowledge. She wishes to prevent him from going to the Senate House because she has been terrified by the supernatural phenomena reported during the night. These phenomena cause Calpurnia to have nightmares. She almost succeeds in persuading her ambitious husband to stay at home, but Decius Brutus uses Calpurnia's dream to persuade Caesar to change his mind and go to the Capitol, where he expects to be crowned king.
This dream is all amiss interpreted;
It was a vision fair and fortunate.
Your statue spouting blood in many pipes,
In which so many smiling Romans bathed,
Signifies that from you great Rome shall suck
Reviving blood, and that great men shall press
For tinctures, stains, relics, and cognizance.
This by Calpurnia's dream is signified.
Portia is not disregarded by her husband; rather, he entrusts her with all his secrets. She is basing her suspicions on the concrete evidence she sees in her own home. It is obvious to Portia that Brutus is psychologically distressed. She senses Brutus and all his visitors are plotting something dangerous. Whatever danger threatens Brutus is equally dangerous for Portia. That explains why she commits suicide after Brutus flees Rome. She can expect no mercy from Antony, Octavius, and Lepidus.
Calpurnia's concerns are based on something less substantial. She believes her dreams and all the bad omens that have been reported. These are easier to disregard because dreams and omens are often unsubstantial. Furthermore, Caesar is so anxious to be crowned king that it would be nearly impossible for her to keep him at home. In Act III, Scene 1, the assassins reenact Calpurnia's dream with uncanny accuracy.
Why, he that cuts off twenty years of life
Cuts off so many years of fearing death.
Grant that, and then is death a benefit;
So are we Caesar's friends that have abridged
His time of fearing death. Stoop, Romans, stoop,
And let us bathe our hands in Caesar's blood
Up to the elbows, and besmear our swords;
Then walk we forth, even to the market-place,
And waving our red weapons o'er our heads,
Let's all cry, “Peace, freedom, and liberty!”
It is noteworthy that there is a conflict between Brutus and Portia in one scene and a conflict between Caesar and Calpurnia in another. Portia wants Brutus to share all his secrets with her, and he resists. Calpurnia wants Caesar to stay at home because it is too dangerous to go to the Senate House that morning, but Caesar ultimately overrules her. These conflicts add dramatic tension to the scenes featuring the husbands and wives. Both women appear to have remarkable powers of intuition.