Surah Al Kafirun - The disbelievers

Sitting on the dock of the bay.
Is this short verse of the Quran mandatory to be read while performing the daily solat? I am curious over this matter just as my late friend Pa' Lah Derus used to make it an issue every time we talk of solats.(Mandatory prayer of five times a day.).
The Surah
Sūrat al-Kāfirūn (Arabic: سورة الكافرون‎) is the name of the 109th Sura (chapter) of the Qur'an. Al-Kafirun means "the Unbelievers."


Like many of the shorter Suras, the Sura of the Unbelievers takes the form of an invocation, telling the reader something they must ask for or say aloud. Here, the passage asks one to keep in mind the separation between belief and unbelief both in the past and the present, ending with the often cited line "To you your religion, and to me mine".
It was revealed in Mecca when the Muslims were persecuted by the polytheists of Mecca.
English Translation by Yusuf Ali:

Say : O ye that reject Faith! [1] I worship not that which ye worship, [2] Nor will ye worship that which I worship. [3] And I will not worship that which ye have been wont to worship, [4] Nor will ye worship that which I worship. [5] To you be your Way, and to me mine.
From what i have read it seems that the Prophet applied this verse during his sunat prayers that is the two rakaats before and two after the regular prayer and he was said to have advised that ti should be recited before one goes to sleep to protect against polytheism. The question is, is it a mandatory verse while one is performing a regular prayer/
I can understand why my late friend was not satisfied with this issue as he noted that there were no unbelievers to be addressed in the mosque when we pray our regular prayers and the One we face and ask any question is Allah. How is that we address in such a manner when facing Allah while performing our solats? Ya! Ayuhal Kafirun, O you that reject faith! I must apologize for my ignorance but it seems rather out of place for this surah to used in the regular prayers just from the fact that it addresses the non-believers and yet many times I have heard it being recited when I am in a congregation as though the Imam has ran out of verses to recite. If perhaps there is more to it than meets the eye I stand to be corrected. I ask this in all good faith and the need to know what is right practice.