Hm. I think I'd feel a little short-changed if I were on a boat on a new (to me) site and didn't get a rudimentary briefing. Particularly if I were paying for the ride. If I don't get any info on the depth, or currents, or what to look out for, it'll be a mite difficult to make a proper plan. In my club, we provide a site briefing for any n00b on an outing even if it's to a well-known site.
Now, if I'm diving from my own boat and exploring a new site, I'm taking that into account for my dive planning. But if someone on the boat has dived the site before, it's just common courtesy to brief the rest of the gang. IMNSHO, of course, and YMMV.