Do people actually know why we say something specific after...?

thanks ...dr tahir ul qaderi ...a great sunni scholar of this eras..auther of over 100 books ...after research ...start writing ..........for ALLAH ..its ok as per your 2 lines quoted.........2] for all prophets....A.S ...and PBUH [for holy prophet ].....3]for holy family [5] /12 imams /their sons/daughters ........A.S.................4] for sahabas /wives of holy prophets..../others contemparories.....R.A....5]for saints ...R.A [ALLAH has his mercy ...on him/her/them...]