When you find an interesting subject surrounded by wire fencing, it can be difficult to get a decent shot. It’s a problem I face most often when taking pictures at zoos, but it can also be a problem when taking photos of old buildings or pet stores (which have beautiful facades, but are surrounded by fences).
You never know when you’ll need to take a photo through a fence. I once had to struggle in the most unlikely of situations (for instance, I photographed some children on a trampoline that was covered with mesh).
You can’t eliminate the fence completely from your composition. It depends on the size of fence wires and the gap between them, as well as the distance you are from the subject. There are ways to reduce the fence’s effect, even if you don’t think so. You can also approach subjects that are fenced in to make it easier to focus.