I think it all depends on the dog.
I started out w/ a crate with Jackson and it was very useful for the first few weeks because it was a place I could put him when I couldn't keep my eye on him 24/7 for pottying. We literally only did the crate thing for maybe 3 weeks, then I purchased an ex-pen that he stayed in while we left. By probably 4 1/2 months old, I put a babygate in my bedroom door and left him in my bedroom. He had full reign of the house by 5 1/2-6 months old. He just never took to the crate no matter what I did and he was always trustworthy outside of it (never once has had an accident or chewed anything while we're not home). So for him, I never felt the crate was necessary. My dad adopted a 1 year old Doxy mix from the shelter so we really didn't know much about his prior history but he's never once had to be crated and was obviously already potty trained because he always went outdoors to do his business so he never had to be crated.