(Assalamu alaikoum wa rahmatAllah wa barakatoh) اسلام و اليكم ورحمة الله و بركاته

Assalamu alaikoum,
I was reflecting about this greeting that is common not only to Arabs but to Muslims around the world. I was wondering where it came from and why Muslims adhere to it so much without straying from it, especially the more religious Muslims who seem to have a hard time even cutting it down to just Salam. I always tried to say it because I remembered an aya (verse) from the Quran that had mentioned that whenever someone greets us we should respond with an even better greeting, which explained to me why when someone says "assalamu alaikoum" many do not just respond with "alaikoum salam" but add to it by replying: "alaikoum salam WA RAHMATALLAH WA BARAKATOH" which means basically and peace be upon u and Allah's mercy and blessings. Here it is:

وَإِذَا حُيِّيْتُم بِتَحِيَّةٍ فَحَيُّواْ بِأَحْسَنَ مِنْهَا أَوْ رُدُّوهَا إِنَّ اللّهَ كَانَ عَلَى كُلِّ شَيْءٍ حَسِيبًا 4:86
Waitha huyyeetum bitahiyyatin fahayyoo biahsana minha aw ruddooha inna Allaha kana AAala kulli shayin haseeban
4:86 But when you are greeted with a greeting, answer with an even better greeting, or [at least] with the like thereof. [105] Verily, God keeps count indeed of all things.

But I noticed when looking up this aya again that it did not specify what words exactly one should say when greeting. So I then asked myself, why then do Muslims seem to insist on using "assalamu alaikoum" and saying it also in Arabic? Why don't we just say "peace" or "hello my friend" "sup dawg" or any other friendly or caring greeting or in any other language for that matter. That is when my good friend said that Assalamu Alaikoum is specifically the greeting of the angels, so what better greeting is better than that?
And he pointed out other places that mention greetings in the Quran, and that is when it made sense for me that Assalamu alaikoum really is the best greeting, and so why not use the best? Here they are:
[6:54]
When those who believe in our revelations come to you, you shall say, "Salmun `Alaykum (Peace be upon you). Your Lord has decreed that mercy is His attribute. Thus, anyone among you who commits a transgression out of ignorance, and repents thereafter and reforms, then He is Forgiving, Most Merciful."

[7:46]
A barrier separates them, while the Purgatory is occupied by people who recognize each side by their looks. They will call the dwellers of Paradise: "Peace be upon you." They did not enter (Paradise) through wishful thinking.

[13:23]
They enter the gardens of Eden, together with the righteous among their parents, their spouses, and their children. The angels will enter in to them from every door.

[13:24]
"Peace be upon you, because you steadfastly persevered. What a joyous destiny."

[16:32]
The angels terminate their lives in a state of righteousness, saying, "Peace be upon you. Enter Paradise (now) as a reward for your works."

[27:59]
Say, "Praise be to GOD and peace be upon His servants whom He chose. Is GOD better, or the idols some people set up?"

[28:55]
When they come across vain talk, they disregard it and say, "We are responsible for our deeds, and you are responsible for your deeds. Peace be upon you. We do not wish to behave like the ignorant ones."

[39:73]
Those who reverenced their Lord will be led to Paradise in throngs. When they get to it, and its gates are opened, its guards will say, "Peace be upon you; you have won. Therefore, you abide herein forever."

and in conclusion, assalamu alaikoum wa rahmatAllah