When I'm working in the Track View and have my tracks set up (using folders or just very few tracks) so that there's an empty space below them, I use my mouse in that area to zoom with the wheel, set Now Time, and make selections (the Smart Tool goes to Select down there).
The reason is that it's a guaranteed "safe" place to click, with few consequences if my finger slips. I don't have to be concerned with accidentally focusing or selecting a track or muting a clip or any of the things that might happen if I clicked in the wrong place in a track.
How about you?
(I'm curious, and I've never created a poll before, so here it is)