Hello...for us it was (and still is) a comfort level knowing that puppy isn't getting into things/chewing things/going potty all over while we're sleeping. And it's all because she's safe in her crate. It's worth its weight in gold, but it's not made of gold.
I've raised puppies both with and without crates… I now use the crates for ALL puppies - and I've got two at the moment (10 weeks and 6 months - plus three adults.
Here's why I use the crates….puppies chew. Sometimes, they have a fascination with bad things like electrical wires; sometimes they like to chew books, or shoes, or baskets and the minute you turn your back they have something they shouldn't between their little piranha teeth. When I'm cooking, or vacuuming or doing laundry, I can put the puppy in their crate with a good chew toy and know that I know that the puppy (and all my things listed above are safe). When I need to go to the bathroom for a shower (or something else , I know that I won't come back out to find that the puppy has piddled on the carpet or worse, chewed a corner of that carpet.
When the puppy is having a mad spell where he/she is biting me and everything else around him/her, and nothing I am doing is working at that precise moment to calm the situation, BEFORE too much blood is drawn or before I lose my patience and handle the puppy a bit too roughly, there is a safe place for the puppy to go to calm down and for me to be able to walk away until we are both ready to try again.
When I leave home, I know that my puppy is safe and secure in her little world that includes a chew toy and soft cuddly toy and a couple of soft towels covered with blanket that makes it feel like the den her ancestors would have made for themselves.
I didn't have all of that when I didn't crate train; I had potty accidents and chewed carpets and destroyed books and bite marks and ……worries every time I had to leave the house….
Our Yellow Baby Girl "Dream A Little Dream" born December 16 2014
Our Chocolate Girl "Kona of the Storm" born August 8 2014
Our Black Boy "Angus Demetrius" born April 26 2013
Our Yellow Girl "Calliope" born January 6, 2006
Our TriPawd "King" - Shelter Rescue born late fall 2004