The patriarchs “rename”—or, perhaps better, identify—Luz as “Beth-el” no fewer than four times (Abram once, Jacob three times). Why? Partly it is because it is much more significant that the place is a House of God (the meaning of “Beth-el”), if it is, than that pagans call it “Luz.” Indeed such a name invites repetition: it suggests a temple.
That is, we must not forget that temples and churches are often called houses of God, and that in the tabernacle and ancient Hebrew temple, the shekinah of God was said to dwell between the cherubim, above the Ark of the Covenant, in the Holy of Holies—in "the house of God." And when Jacob returns to the place, he builds an altar that the Lord told him to build (35:7). Thus, this appears to be an early form of temple, complete with sacrificial altar and the nearby sanctum, duly anointed, where the priest would interface with God, as Jacob, God's anointed, did.
Very well. This still leaves unanswered the question why Jacob apparently “renamed” the place as “Beth-el” (or, once, “El-Beth-el”) three times. But first I want to ask, "Is that what he did—renaming?"
A bit of background sheds light on this. The place of Jacob’s ladder is the same Beth-el as that at which Abram first built an altar (Gen 12:8); suffice to say that there is plenty of evidence of this elsewhere, and it would be tedious to prove it. The only reason for doubting it is that the text states that Jacob “called the name of that place Beth-el” (28:19)—yet it was previously called that in the text. So, why would he name a place previously named?
The problem is reminiscent of Isaac’s re-christening Beer-sheba after Abraham had explicitly named it (see 21:31 and then 26:32-33). There the explanation is that Isaac gave the wells his men re-opened their former names (26:18), thereby reclaiming them.
So here I propose a somewhat similar explanation. While there was a city probably very close by called Luz, Jacob instead chose to call the place of his dream in Gen 28 “The House of God,” “rechristening” the spot. This was in accordance both with the dream he just had, and with the family’s traditional name for the place, which probably began with Abram. It is as if Jacob said: “This shall remain our name for the place—not the unholy Canaanite ‘Luz.’”
When Jacob returns to the spot some 30 years later, he gives it the newer variant name “El-Beth-el,” meaning “God of the House of God.” This is yet another instance of a patriarch giving the same or a similar name to a place previously named. Other instances include Abram’s original naming of Luz to Beth-el, Isaac rechristening Beer-sheba, and Jacob himself first calling the place “Beth-el” after the dream of the ladder.
But here I would like to add another conjecture: rather than rechristening the place, Jacob is reidentifying it, perhaps for the benefit of his family, as Coffman‘s commentary suggests. It is as if Jacob said, “Yes, this is indeed Beth-el, the same that I visited 30 years ago.”
Still, this leaves unanswered why he called the place by—as it were—a name of God. That is, “El-Beth-el” resembles in form “El Shaddai,” for example. Is that really how we should understand the place’s name? Perhaps; I suppose it might mean that Jacob is representing God as filling the place, so that to point to the place (maybe especially the altar) is to point to God. But it is also possible that this was just a method of adding a second “El” to “Beth,” honoring God through repetition, as in the “emphatic plural” or “plural of majesty”. I do not know whether this is actually how the emphatic plural actually works, however.
Then, as if to make the matter maximally confusing, Jacob is yet again (for a third time) shown naming Beth-el as such (35:15), though this time without the prefixed “El-”, as at 35:7. Why? As we have seen, this is no mere random place-name. As a "house of God," this place is like a temple, and thus honors the God who has just appeared to and blessed him yet again (35:9-13). And notice: this final instance must make it very clear that we must not be confused by the construction “called the name of the place”. That phrase simply does not mean “newly christened the place,” as you might think if you took the verse on its own, out of context. No, "called the name of the place" means, rather, “praised God (again) with the honorific for the place.” The honorific was traditional for the family by then, but was just now given renewed, deep meaning.