Well thats not my experience. People just keep them on their desk near the monitor. Of course I really don't see too many people buy Minis these days unless they adapt them to be home media servers and not as desktop computers. The mini is also not a tower. Nobody would seriously classify it as that.
So what's the difference between leaving a mini out and leaving a tower out? None. I would be perfectly happy leaving a nice looking tower out, just as I'd be happy to leave a mini out. I also wouldn't feel bad if I needed to tuck the tower away, just as I don't feel bad tucking a mini away for space reasons.