It's not just about the free candy, although that's a big part of it.
It's about the experience. The thrill of watching a grown adult try to get the last quarter out of the gumball machine. The satisfaction of seeing a child's eyes light up as they realize they can actually play a decent game of Pac-Man on the thing.
But let's not forget the real reason we need an arcade machine: the committee members' own personal nostalgia for the good old days when they used to spend all their quarters on Galaga.