Bill Gates might rather cure river blindness, malaria and cholera. He's at that stage when a billionaire thinks about humanitarian legacy. Similar to Andrew Carnegie and the moguls of that generation.
There have also been some cogent arguments that it might be in the best interests of our own self-preservation to not broadcast our presence, for now, just because we are still technologically primitive. Being loud represents a big wager that anything else within hearing distance is friendly.
I'm mostly disappointed at this announcement because it is part of a trend in dwindling government support for exploration.
Putting it simply for the first time it would be us and them where us is our species rather than the us that happen to be on an arbitrary lump of earth, speak the same language or worship the same god.
It could be the next psychological development stage for our species as it grows up. I'd like to have my name associated with that.
We have barely uttered a sound in the universe.
Of course, light goes really, really fast compared to anything physics says we can possibly manage for things with more rest mass than photons. Although there could be aliens on another spiral arm, or Andromeda, communication would take longer than the lifetime of our civilization; and material trade would take longer than the lifetime of our species.