Have you ever been to a Reform wedding and the Rabbi undoubtedly ends up

I haven't, but I've been to services where many non-Jewish students were present, whether it was friends of a bar mitzvah or a comparative religions cl, in which the rabbi took time to explain why certain prayers were said, and their significance. I can imagine the rabbi at a wedding with a lot of Christian guests explaining the unfamiliar ceremony to them. And then, high holiday services, when everyone is there for once, is a traditional time (in my experience) for rabbis to talk about why you should be there every week, why Shabbat is important, and to work the basics into a sermon given to folks who may not know them because they don't regularly attend.