For me, I find it almost region specific. My last wedding was in Pennsylvania, and there were a few men there who just showed up with khakis and polo shirts. Grooms men and Groom were tuxedos!
Most of my weddings I see men wearing suits with tie, but some men opt to not bother wearing a jacket, and then some don't even bother putting a tie on, just the button up shirt open collar. I don't think The couple or their family really cares how the guests are dressed as long as they aren't sloppy I am assuming.
At most of my weddings, I am seeing photographers dressed pretty casually these days. Men are usually wearing polo shirt, or button up shirt, but I don't see them wearing ties any more. Years ago, the photographers use to dress in tuxedos! Not sure what changed except perhaps the culture among photograhers in the last 15 years. Caterers are usually in all black, but sometimes white shirt and tie. Sometimes, just black polo shirts depending on who they have catering.