It's because I've done laundry by hand and decided that I love my washing machine, and will never be voluntarily parted from it. It's one of the efficient ones that uses less soap, less water, and less electricity- and it gets my clothes clean without backbreaking labor.
I'll admit the dryer is handy for the bulky things that don't do well on the line, and for the times that you need THAT particular set of clothes NOW. However, my dryer gives me seizures every month when I get my electric bill and find out that my DH did laundry and used the dryer for everything.
Marital discord aside I've mentioned before that I live in a place with an excess of hot, dry and sunny. To my mind, this is what laundry racks are good for.
I've got two of this kind, and not only do they hold more laundry than you'd think, they fold up flat and are easy to store. I like that I can use them outside if it's sunny, and in the winter I can set them up inside. The wet laundry helps humidify the air in the house during the wintertime, too.
I also have a little hanging rack kind of like this (I got mine from the dollar store, though) that's handy for drying socks and baby clothes. This usually gets hooked over the shower curtain rod in the bathroom when it's in use.
DH also set up an outside line for me. I'd had one of those white vinyl laundry lines, which of course got all stretched and eventually broke. He went to the hardware store and got me a length of narrow gauge steel cable coated in clear plastic. He may tend to overbuild things sometimes, but I can and have dried the living room rug on that line.
