Why should we take the dogs out?
Does your dog spend hours outside with you, or, does he know only the yard at your house?
Imagine this scenario - you would be locked up at one space for a whole year. You wouldn't have any idea how "the outside" looks and what you can expect in there. You wouldn't communicate with people, you wouldn't have phone, internet, nor TV. You would have no overview of the outer world what so ever. It must sound like a horror to you, right? How would you feel? Probably bad, frustrated and anxious...
The horrible vision above can be exactly the same for dogs too. They can also feel frustrated and anxious when you leave them in the garden or at home only with words - "he has the whole garden for himself" or "he can use every room at home". Even though dogs have enough space around them, it does not necessarily mean they're happy. It's not all about the size of their space, they need interaction!
Dogs usually sleep throughout the day and they just wait for us to get home. Sometimes, when the dog is alone for long hours, he can get anxious and bark, howl and maybe even try to escape. You should try to avoid this by taking him out regularly, so the dog remembers that when you get home, he's going out.
Dog is like a curious child. He wants to explore the whole neighborhood, meet as many furry friends as possible, sniff every corner and read all the messages others left him. By this he's learning and taking in the experiences for next time. When a dog cannot socialize like this, he can be nervous and shy, skittish or aggressive because of his fears.
So, remember, the garden or a big house cannot substitute your walks outside. Take your four-legged friend for walks from puppy age. Visit dog parks, walk through nature, forests or meadows, introduce him to order animals, take him to the store or restaurant, and meet a lot of people. Give him space to adjust, encourage him to explore it all and you'll see it's going to pay off later. Your dog has to know the human world to be prepared for every situation.