I'm guessing it's a safety issue...they're so small and they don't see well if they have big topknots with all those feathers in their face.
There are different degrees of "free range". I fenced in an area of my property to let my 13 chickens (including silkies) "free range" so they can eat grass and weeds and chase bugs and sit under the bushes, etc. They love it, but they're still relatively safe because they're fenced in.
Right now they are locked in their run (16'x16') because I'm dog-sitting for a friend....poor chickens hate it....they're used to more freedom than this.
I started with 7 Silkie chicks last summer. When I figured they were big enough not to be a cat snack (around 3 months), I let them out (supervised at first) in the yard. I had 5 cats last summer, but had no problems with any of them bothering the chickens. Usually let the chickens out late afternoon, but as time went on, I would let them out all day. The silkies and my buff orpingtons all were out in the yard (when I was at home) with no problems.
I let my silkies out in the evening to roam my backyard. i have made sure that there is cover for them to run to in case a hawk flies over. However I dont leave them to roam when I'm not at home. They get locked into their run with access to treats, feed and water.
I don't let my silkies roam, they seem to have a hard time making it back into the coop at night. My eldest daughter accidentally let one of my hens out and I couldn't find her until the next morning. She was all wet and shivering (she must've had an encounter with my creek). Its just not worth it to me to lose one of them so they just hang out in the coop and the attached run.
Sure, mine are working on 10 weeks and they have been going out for about 4 weeks. Our coop is under some trees and they stay along the tree line. We let them out when we get up and they are always back by themselves around 8:30. We have a ton of eagles in fact one had my older girls trapped under the motorhome last week but they all seem to have the instinct to stay under the trees, along the house and fence lines where there is cover. No problems so far. Fingers crossed!
I just got three 4 month old silkies this weekend. For the first 2 days they had NO interest in free ranging in my front yard. Now that they have acclimated somewhat, they are out and about happily scratching, pecking, and romping with everyone else. I do have to pick them up and set them inside the coop when it's raining though - they are oblivious to it. We only let our birds out when we are at home for the day. So they are supervised by me, and even when I am working on stuff or cleaning house and whatnot I check on mine about every hour to be sure all is well. We also have fruit trees aplenty in our front yard and lots of low bushes - like black raspberry and whatnot - lots and lots of cover. We have had no issues yet, and my other "babies" who are younger have had no issues so far. Time will tell.....
It's really a matter of personal choice, and I totally understand why some do NOT choose to free range their flock. We are prepared for the likelihood losses, and still try to do eveything to keep them safe while allowing them lots of excercise and freedom. And, IMO free range eggs CAN'T be beat!
I let my Silkie roam around the unfenced yard while I'm home. Sometimes I have to pluck her out of a neighbor's yard, but they don't mind her there. Because she can't see through her fluff, predators are a HUGE threat. My cat would stalk my Silkie, run and puonce and do that "raawr, I'm a scary tiger, prepare to play!" thing, and Phyllis never even reacts! Bummer for the cat, bigger bummer for the bird if it had been a hungrier cat.