I think it really depends on the breed, determination and age of the chicken as to how well they fly.
I have five bantams.
I am in a residential area with low fences so when I purchased the original two, I clipped one of their wings (if you clip both wings, they apparently can still fly quite well. If you only clip one it makes them a little lopsided which causes a flight-balance issue).
I have not had to clip their wing since as they have no urge to leave home. I kept two chicks from two separate hatches and also recently bought a Frizzle Pekin. These three have not needed their wings clipping as they have learnt the boundaries from the older gals.
I clipped four of my six girls wing's two days ago because they're such flyers and they're only 7 weeks old. If you need to cut the wings and you're own your own like how I was, hold them still with your pointer and thumb touching, making a circle around their necks so that they don't move back or forward, push their body into your stomach area to hold down their other wing, and with the same hand that's holding their neck, hold their wing that you're going to cut out. You kinda have to hold their wing tight, since they'll pull away and fight with you. Clip ONLY the primaries since the secondaries have blood feathers and can hurt them ( I don't really know if it's the same on chickens, but I had an inexperience man trim my cockatiel's flight feathers and he bleed and never flew properly ever again. NEVER AGAIN will that happen to another one of my birds!). The chicken will struggle a bit, but talk to the in a low voice, pet them for a bit, let them calm down again, and trim the feathers when they're relaxed.
The vet clipped our Americauna's wings today after stitching her back together after the dog tore her up. She's a very light bird and flies over the fence that contains the others with no problems. It was clearly a disaster waiting to happen and I'm angry with myself that I didn't do it sooner. I don't think it needs to be done automatically, but if you've got one that flies like this and there is danger nearby, then I think you should seriously consider clipping it's wings.
The primaries also have blood vessels in them when they are growing. After a molt you have to be really careful if you decide to trim. Look at the feather shaft of each feather you are going to cut. They should be completely clear or white. If there is any dark color to them the blood vessels is still feeding the feather and you shouldn't cut it or you'll have a bloody mess. The only way to stop the bleeding is to pull the feather out.
My hens can fly at least 5 feet high. When I got them I assumed they couldn't fly out of a stall with 5 foot walls. When I got home the next day they were running around the driveway. I keep them fully feathered since they are free range and I want them to be able to get away from a predator should one ever come after them.