When you're taking pictures do you wish you could get closer? If you do, you need a telephoto. Do you wish you could get farther away? Then you need a wider-angle. A lot of it has to do with your personal needs. At one point I was lusting after a wide angle lens and I went to a file of photos and looked at the shots. I found that by far the shots maxed out at the wide end and not the longer end. I decided I wanted the telephoto but needed a wider angle lens.
Generally, I use wide-angle lenses for interiors of buildings, land and seascapes. I use telephotos to move in and get details.
There are those who say, sometimes quite snippy, that you can just use your feet. That's true but standing in heavy traffic while I take a picture is distracting and getting up close and personal with a bear isn't advised.