Sometimes a performance is best experienced with other people. The real advantage of television - that theater and the movies don't have - is you're allowed to talk through it.
It's a policy to honor donor intent. It's a double-edged sword and it's one we don't like to have to encounter, but we understand and do our best to let people know we've reached our fund-raising goals in those instances.
Where else would you do this? If you do this in a serious venue, it would sound smarmy, produced and self-conscious. The best way to get out of (trouble) and get a few laughs is to have a late-night comic helping you through.