It'd work backwards though.
Normally people would stop watching when the award show ends because, you know, who the fuck likes to watch telethons? But if a celebrity's speech goes long, the media would jump on the exact point you are making, and information about the telethon's cause would go viral as the long-winded celebrity is shamed. So that the strategy for a charitable celebrity would be to either be brief in their speech and let the charity go ignored, or to sacrifice their good-name to all the bile and outrage that goes with a headline scandal and thus insure that the charity gets heaps of attention. This would be tricky too, because if all the celebrities went for the scandal method, it would get stale eventually and stop being effective. So that there would be an tactical aspect for the willing celebrity martyr, where they have to consider how long it has been since a similar scandal, and whether or not an award show filibuster would be worth the trouble in the end.
Which is to say you've just turned acceptance speeches into a complex game.