Wow there's some skooky stuff in this thread
Well, a lot of it is cultural and not easy to say what will really change it. Especially in the modern day, a lot of the wedding extravaganza has roots in consumer culture and a very USonian propensity for personal indulgence. Anything that will weaken traditional views of what marriage should look like (feminism, influential media, backlashes, etc.) and encourage austerity/discourage materialism (economic stress, war mobilization, etc.).
Kneecap the Progressive movement, and keep significant inequality, high tariffs, and isolationism more prominent could limit the industry to the wealthy and aspirationally wealthy.
Keep the social backlash of the 1970s/1980s to a minimum, keep deregulation from opening the floodgates of consumerism, and keep the US economy tottering along not too bad but not perky either.
Have the Dubya 'compassionate conservative' coalition fail and have the dot Com bubble burst ache a little longer. The social movements changing our concept of marriage are not kneecapped by the Bush administration, and thought 9-11 and War in Iraq are not guaranteed, it's likely Gore/other president would wind up trying to accelerate the end of history somewhere.