Q. Why does the bensching (Grace After Meals) at weddings and Bar-Mitzvahs take so long?
If the religious part of the celebration, which after all gives the occasion its Jewish flavour, takes a few minutes, why should anyone object? After all, is it not precisely at a simchah that family and friends should want to voice their thankfulness for all the blessings God has given them? Indeed, there might even be an argument for extending the bensching, not curtailing it!
Yes, there is a short form of grace found in the Siddur, but this should only be used when time is genuinely short. As a general rule the full version should be said, with everyone paying attention and joining in wherever they can. On rare occasions the leader of the bensching drags it out and makes it an operatic performance, but most officiants have more common sense.