Because almost all spiders are good for the enviroment ! The Black Widow and the Brown Recluse are dangerous, but all the rest of the spiders here are good to have around ! Nothing to be afraid of ! They sure won't hurt you. They're more scared of you than you are them!
Well, looks like you have arachnophobia. The fear of spiders. Just think of it this way, spiders kill other harmful bugs, so if it weren't for them, we'd have quite a few bug problems. Trust me, they're probably afraid of us than we are to them.
Study them. Learn as much as you can about one species in particular, or all in general. By becoming familiar with them you will lose your fear. When I was 4, I had several wolf spiders fall on me, I became terrified of them. Since I wanted to "know my enemy" I studied everything about them, after a few years my fear was gone. It was replaced by a sense of awe about the natural world. :)