Drops afford more options, one of which is to ride down in the drops in a headwind, reducing wind resistance. I spend most of my time on the tops of the bars because it puts less pressure on my hands and arms and is more comfortable on my back - either on the straight part next to the stem or on the top of the first curve. But I'm not averse to spending extended periods down on the drops, just for something different.

On my mountain bikes there are only a couple of hand positions I like - either on the grips or on the bar ends. I have curving bar ends and can put my hands on top of the curves, but I don't really like them up there.

For trail riding, the flat bars make sense, but for road riding and touring, give me drops.