The word "Khash" on the bed

Peace and blessings!
The words of the Magen Avraham, the sign of the Relat sec.
"... And in truth, the psalms are not obligatory at all, only the Shema and the Mifli, only those who are accustomed to saying them, are the ones who
According to this Maga, this obligation is only on the one who misled and heard. 
There is no point in abolishing the custom as long as its purpose is not abolished (Maga 31, section 22), but here, since the issue is protection from harm, I wondered to myself, would it be possible to say nothing except for the hearer and the one who rejects? This is of course assuming that the hearer and the one who rejects are not only concerned with protection, but rather because of the biblical meaning of "say in your hearts," as it is written in Berakhot 4:2.
Moreover, in the middle of writing these lines, I saw that the Maimonides omitted the matter of the psalms:
Rambam, Laws of Prayer and Blessing of Priests, 7

Halacha A
When the Sages established these prayers, they established other blessings to be recited every day, which are:
When a person enters his bed to sleep at night, he recites the following blessing:
"Blessed are You, Lord our God, King of the universe, who casts sleep upon my eyes, and gives sleep to the eyelids of the eye. May it be pleasing to You, Lord my God, that You save me from evil affliction and evil harm, and may I not be frightened by evil dreams or evil thoughts, and may my bed be perfect before You, and may You raise me from it to life and peace, and enlighten my eyes lest I sleep the sleep of death. Blessed are You, Lord, who illuminates the entire world with His glory."
Halacha in
And he reads the first portion of the Shema and sleeps, and even his wife sleeps with him (he reads the first verse or verses of mercy and then sleeps).
And if he is forced to sleep, he recites even the first verse or verses of mercy and then sleeps.
thanks!