Okay, so one of the reasons is that we don't actually have a drier (we have a very bad one, hardly counts), but even when it was available to me in the past, I would still hang-dry my laundry whenever possible. All you need is a bit of dry space and a line or rack to hang up the clothes.
How long does it take? I'd say about 5-10 minutes. No more than that. You get more efficient too as time goes by.
So why would you opt for hanging up the laundry instead of just popping it in the drier? Here are my main reasons:
Using the drier takes up a lot of electricity. You're wasting electricity where you could just use the air around you to accomplish the same job. Even if it takes a little longer, after you hang up the laundry, you don't have to look at it until you take it down.
Running a drier costs money. You have to pay for the machine and for the electricity. Wind/air is free! You'll even notice the effect more directly if you usually go to a laundromat that charges for the drying.
Laundry that has been machine-dried just doesn't absorbed water quite as well as laundry that you dry on line. That's also the reason I don't use fabric softener (actually, the previous two reasons are also good for not using softener: they're expensive and entirely unnecessary chemicals. Yuk!)
When you hang-dry the laundry, it dries at room temperature. That means you don't risk shrinking it because of the heat in the drier.
The lint from one sweater isn't swirled around and automatically transported onto every single other item in the drier. I made the mistake of putting one of my sweaters in with some sheets once and was never able to get them quite lint-free again.
I can't stand static. My hair goes in crazy directions and you end up with handkerchiefs stuck to your jeans while you're running out the door. Static may be harmful to your body as well as uncomfortable.
What about you? Do you use a drier? Ever considered using a clothes-line instead? Is there something that prevents you from doing so (bad weather, small apartment)? Perhaps we could figure out a solution together!