The Special treatment to Sadat who are the grandchildren of the Prophet Muhammad ( SAWA) is based on the respect and love to the Prophet ( SAWA) and his Holy Progeny ( AHLUL Bayt) (AS).
The great services rendered by the Prophet and his Ahlul Bayt to the whole Muslim Ummah can not be thanked at all by us, but Allah (SWT) has told the Prophet in Quran to tell Muslims : I do not ask you ( for my efforts ) any remuneration but only the love and kindness to my Progeny. ( Sura 42, Verse 23).
The Prophet (SAWA) told Muslims : Love Allah for what he is showering on you from His bounties, and love me for the love of Allah, and love my Progeny Ahlul Bayt for my love.
( Tirmithi , number 3792,
and Al-Mustadrak by Al-Haakim 3/150)
He also said in another authentic Hadeeth : No one from you Muslims will be real believer in Allah until he loves me and my Progeny Ahlul Bayt more than his love to himself and his family.
Kanzul Ommal 70/91.
We must show our respect to the grandchildren of the Prophet (SAWA) and Ahlul Bayt (AS) for the sake of Allah and love and respect to the Prophet and Ahlul Bayt.
Poor Sadat are not allowed to utilize Zakat from people, that is why Allah has kept for them the right in half of the Khums as far as they are really needy.
The history of Muslims has hundreds of incidents of the sufferings of Sadat by the enemies of Ahlul Bayt and it is still going on in many places.
Respecting the grandchildren of the Prophet and Ahlul Bayt is one of the signs of real Faith and respect to the Prophet and Ahlul Bayt.