What is the meaning of the "narrow" road/path metaphor?

All my life, I've regularly heard phrases such as:

Walk on the narrow road, never steering off into Hell! Don't listen to the Devil trying to lure you into his dark path!

This, to me, metaphorically means that one should do good (not evil), by walking and staying on the "narrow road/path", and that the "other" road/path, supposedly much "wider" (opposite of "narrow") leads to damnation and bad end result, even though it's easier to walk on.

But this metaphor is very confusing to me. You'd think that the right path/road is the wide, easy one, and that the "other" path is like a narrow little side-path full of dangers, albeit attractive somehow, such as a beautiful woman with devil horns and a hidden tail trying to lure you onto a small country road to rob you.

The metaphor seems to fall apart if you try to apply it to some sort of realistic environment, which to me makes it a bad one. In reality, should one not use the main road most of the time, and only take "narrow side roads" if you have a special reason to do so? Isn't it much safer and less problematic to walk on the wide road as opposed to a side-path where barely anyone walks?

I don't feel like I'm describing this as well as I'd like. The metaphor seems "reversed" somehow. Why would the righteous, good, non-evil road be the "narrow path"? Is the insinuation that most people and the general public are all evil scumbags and they (almost) all take the big, wide road, and it's not the devil standing there at the side, flipping a coin with a big smile, but rather an angel with a halo, desperately trying to talk you into taking the "narrow path"?

I could never understand this and I've many times seen it used in a way which I assume must be wrong. It certainly managed to confuse me. Would love to finally hear the "original idea" behind this metaphor and how it makes any sense for the narrow side-road to be the good path to take.

The Biblical reference is explained in Matthew 7:14, see Wikipedia. In the King James Version of the Bible, the text reads:

Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.

From the Wikipedia article,

The metaphor in this verse implies that the path of sin is an easy one to follow, and that one will do so without conscious effort not to. Davies and Allison note that the notion of vice being a far easier path than virtue is a common one to most religions. The verse seems clear that it is only a minority that will find and follow God's path. While pessimistic, this is in keeping with Jewish thought, which traditionally saw the pious as a beleaguered minority in a world of sinners.

The article references a work: Davies, W.D. and Dale C. Allison, Jr. A Critical and Exegetical Commentary on the Gospel According to Saint Matthew. Edinburgh : T. & T. Clark, 1988-1997.