Why does the sun go down in the west? Can be answered.
But why is gravity? does not make sense.
Your confusion, it seems to me, and i mean this will all respect, stems from the fact that you are seeking a quality in things that are simply not there. It is a perception problem. Some of us know that that quality is simply not inherent in that body or system or function; some of us come from the belief that EVERYTHING happens for a reason, which can be pointed at when answered if you ask "why". Then when they encounter things that can't be answered, they are baffled just like you.
For your sake, I wish there were a reason that would answer why car engines work. They certainly don't work to make humans' life easier, or to make the inventor happy, or for for more pay. They just do work, without an underlying reason. I wouldn't even call it spiritual reason; just a reason that would give meaning to their existence, if car engines were sentient.
I suspect your romantic sense in searching for the why in everything is due to your background. I used to know a feller from some Arabic country, a brilliant man, very highly educated, but he was lost in the cruel morality of the western world, because to him the "oughts" had much more punch than to us, his western friends. He was a direct hit with the ladies, or would have been, but he, unlike you, was impertinently forceful and overbearing, and women don't like that, although some would.
I met another feller in that bunch of circle of friends, he was also from the east, form India, and he could talk magic, so to speak, women loved to listen to his flowery thoughts. It's not that his language was flowery, and his thoughts normal or mundane; it was his very thoughts that were flowery. Women fell over him all over the place, and our suspicion was, in the circle, that he was gay, living in the closet. But those women who acknowledged this suspicion, still thought he was a gift from the heavens to womankind.
I had terrible bouts with him. Not because he was rude or overbearing or something, but because I was in a different phase at the time, and I really fought to have my weltanschauung accepted by everybody. Each time he proposed something which I found impossible or against human nature, I would voice my opinion without hesitation. Now that I'm older, I am calmer, and more accepting -- but it came at a price. The price was to have grown old, and have my testosterone production cut down tremendously.