Yes, it's important to take your dog out to relieve himself. In fact, every 5 or 6 hours during the day your puppy HAS to go. The importance of walking your dog has to do with a lot more than peeing and pooping though. Unlike us, a dog's most powerful sense is smell. Up to 40% of their brain activity is designated for discovering and interpreting scents. Just look at the above illustration of the nasal cavity. It's gigantic!
Whereas humans can only detect the most prominent smell in a room, your dog can simultaneously smell the furniture, your shampoo, what you had for lunch, what's in the garbage can, that cat that rubbed against your leg 4 hours ago, and the mud on the bottom of your shoe. When you take fido for a walk, it's like a smorgasbord for his brain. Every patch of grass is exciting to him. I would imagine it's akin to reading a good book or seeing a movie. Then he gets the added bonus of meeting other canines on the walk. Oh boy, how great is that!?! (Please note: This post is dedicated to those dogs without reactivity issues. If your dog is reactive or nervous around other dogs, then the walk will be anything BUT calming and rewarding.)
A dog's second most prominent sense is hearing. He can hear 4 times farther than you and more pitches. Trapped in your home all day, your dog gets bored. Same scents. Same sounds. Boredom leads to anxiety which leads to unwanted behaviors (i.e. ripping up shoes, compulsive grooming, excessive barking, etc) and your dog becomes unbalanced and unhappy. He needs to burn off that excess energy and pull in some new experience to his consciousness.
The walk is also an opportunity for bonding with your dog. In the dog world, they don't sit around and bark at each other to relate. They are active. There is something that I like to call "the zone" that happens on a long walk. Your dog gets in rhythm with your steps and both of you are silent and you begin to feel like you are moving as one unit. When I'm working with dogs, I notice a shift in their willingness to learn after we've had a walk "in the zone". This state of being is heaven to your pup. You are bonding with him.
Remember, you don't need to chat. Your being relaxed and walking with him is more rewarding than you could ever imagine. You are taking him out of our artificial world of computers, t.v., loud noises, etc and bringing him back to his true habitat: the outdoors.