It's absolutely crazy to not use a torque wrench on a bicycle. IMO, it comes down to liability. I don't care how much experience a mechanic has, you can not feel 6 NM consistently. Secondly, when you're in the middle of a disposition, a lawyer will tear you apart when you say, "Oh, I've been wrenching for 20+ years and I know how tight it should be."
I have friends that work for Boeing that have to use USB Torque Wrenches for liability purposes. CYA, amigos.
First off, I just wanna make clear that I'm no mechanic. Secondly, I take no notice of recommended torque specs. As the previous poster mentioned, these are max recommended specs. I certainly let common sense rule, in some cases I go lower and in some.cases I may exceed it. What I mean when I use feel, is not that I try to feel out what Nm number I've reached, I rather feel out what seems sensible for that particular part, taking all data I can into account. I.e what mounting paste or grease, material and quality of the bolts, I will go lower torque on low quality ti/alu bolts than on equal construction but higher grade bolts. I will also take into account the construction and composition of the rails, bars, steerer, or what have you...
As said, I'm not recommending others to follow my example. I'm just saying there are other ways, and this blind belief in torque wrenches may save you from a law suit, but that doesn't mean anyone can build a bike properly just because they have a torque wrench.
A torque wrench will not make a mechanic out of a monkey, but it may take the common sense equation out of the mechanic.