I've sat through two weddings where the pastor chose to share that passage. One time it was without commentary, and the whole ceremony came across poorly to me

I've sat through two weddings where the pastor chose to share that passage. One time it was without commentary, and the whole ceremony came across poorly to me (he even solicited conversions to his church at the end, as if it were a public Sunday service). The other was a younger guy who didn't say the whole thing and tried to explain it away the best he could as more or less being about "supporting each other". I liked that wedding a lot better in general, but I still think that's a terrible passage to recite during a wedding. So if pastors think that is the most important bit to share when performing actual marriages in public, you shouldn't be surprised that this is what people are most familiar with.