Never. There are a few reasons I do not bring dance floor lighting.
You don’t want your DJs wedding setup to look like a high school homecoming. This is an adult event – not an 8th dance. The venue is going to look great and your DJs setup should compliment the room. Lighting up a dance floor requires that the lighting fixtures are hung in the air so it projects over people. Well, that is awfully ugly for a wedding don’t you think? People walk in and see a bunch of lights hanging in the air from tripods or worse a big ol’ truss that spans the entire DJ area. It’s a wedding. Not a Mitzvah. Lighting fixtures junk up the place. No good.
Aesthetics are not the only thing saved by the absence of dance floor lighting. Great moments captured by your photographer of people having fun are completely ruined. You have these spectacular candid shots of people letting loose and having a ball only to be ruined by random dots of color everywhere and all over everyone. Huge disappointment.
That is where uplighting creates an elegant and fun atmosphere while being unobtrusive in your pictures.