The main point where a torque wrench is needed is when you are clamping on carbon. In that case, the spec is very important because over tightening can crush the carbon and cause a failure. That said, common things like seatpost clamps and stems on carbon parts almost always need something like 5 or 6 nm which is easy enough to do by hand. In the shop I was at, we had pre-set Bontrager tools laying around and it was really easy to grab those every time we did a headset adjustment and needed to tighten the stem. If for some reason I had to do it on the side of the road, doing it by feel wouldn't be too far off having done it hundreds of times on various bikes.

That said, there are lots and lots and lots of bikes with alloy bars, steerers and seatposts. At that point, precise torque specs aren't required as much as common sense is needed to not go ham fisted on it and to make sure each bolt has even tension on things like a stem. 90% of the time it's tightening a stem on a carbon steerer or clamping a carbon seatpost, and in that case it's super duper easy to just grab the preset tool I mentioned earlier.

The only time I remember pulling out a real-deal torque wrench was generally for Shimano Hollowtech cranks (and there it's less the crushing of the spindle issue as much as it is making sure both bolts have even tension without going so tight as to over stress the bolts), Campagnolo ultra-torque cranksets (with a single bolt holding it together, you kind of want to make sure i'ts done right), and weird aero seatpost setups where you couldn't use the preset tool due to clearance issues.