You raised a very good question. We really want to know its answer. This is our QUESTION to you, which you are asking US. That why don’t we see, saying Ayesha (Aleyha Salam) and Usman (Aleyhi Salam).
The status of Ali(AS) is not because of marriage with Fatima(AS), however Ali(AS) himself considered it as a great honor. Prophet Muhammad(PBUH) married Ali(AS) with Fatima because of his status. Read what Prophet(PBUH) said in the following AaHadith. You misunderstood this. Marriage or relationship does not make the status itself. Specifically that status which is blessed by Allah.
Imam Sadiq (A) said:
"Do you know the explanation of (the name) Fatima?
I said:
`Inform me my Master.’
He said:
`She is safeguarded from evil.’
He then added:
*`Had AmirAl-Mu’mineen not married her, no man on earth from Adam on would have been suitable for her until the Day of Rising. *
This narration was also reported by a group of Sunni scholars, among them being Ibn Shirooyah Ad-Dailami who said:
"Um Salamah said: 'The Messenger of Allah said:
`Had Allah not created Ali, there would not have been an equal to Fatima.’
Besides Ad-Dailami, Khawarazmi in Al-Manaqib, Munawi in Kunz al-Haqaeq, and Qandouzi in Yanabea al-Mawaddah have reported this tradition by quoting Um Salamah and Al-Abbas, the Prophet’s uncle.
Fatima Zahra(AS)
http://www.al-islam.org/gracious/9.htm
http://www.al-islam.org/gracious/26.htm
Its not only US. It is the practice of all Muslims. Except those who are working against Ahle Bait(AS) and their Imams(AS). I asked you before to ask your Ullema, read their text, their old books. They were all using Alay Salam for Ali (AS) Fatima(AS) Imam Hassan (AS) Imam Hussain(AS).
If you want to discuss the about infallibility of Prophets (A), Imams of Ahle Bait (A), Angles and great personalities who were infallible in the history of man kind like Marrium(AS), Sara(AS), Hajira (AS), you can either start a separate thread or you can refer back to those threads and link on which this topic is discussed in detail.
**Note: For K-2 Question pertaining any Hafiz among Shia Muslims is discussed in my previous post. please scroll up to see. **