Ah cool! See, I never knew that, 2.78 turns of the wheel for each turn of the cranks. I see what that means now. But really, that never mattered to me and never even thought about things that way.
Well, the actual mechanics does matter to you, even if you don’t think about it. On a 1:1 ratio, even riding around the block would be tediously slow.(and the reason for the invention of the Penny-Farthing bicycle). On a 1:10 ratio and 700C wheels, you’d struggle even to get going. If it truly didn’t matter, you’d be entirely content staying in one randomly chosen gear all the time.
But sure, the main use is for comparison. Once you have a bicycle you’re happy with, and isn’t planning to switch, this can be entirely ignored.
Heck, I had a cadence meter in the past. Found I had a high cadence, about 95 rpm. Even that was interesting for about a week. Then after that, I never even looked at my cadence at all. I just know it's high enough to be efficient.
Most of my body considers itself a masher - low cadence, low gear, high effort. That was all fine and well until the knees registered an another opinion and submitted their veto to further riding. Took me years to recover and kinda-sorta retrain as a ”spinner” instead. And while I’m now fairly well settled on an average cadence that’s 10rpm higher than before, I tend to fall back onto old, bad habits when I get tired or distracted. A cadence meter helps to keep me riding right.
Maybe the turns of the wheel for each turn of the cranks is important to the touring types? I've heard them talk about 1:1 set ups before.
It isn’t the number as such that’s important, it is to have a recognizable comparison point. Since human bodies don’t come with a registered grunt-o-meter that lets us compare how much effort something takes, we have to find other ways around If we want to be able to hold sensible conversations about what works for a certain ride.
BITD before MTBs, 1:1 gearing was as low as you could get on a stock bike, and quite important as such for loaded touring.
But sure, gear inches, or meters development, or mph at a set cadence would all work equally well. It’s all down to the same thing, establishing a recognizable comparison point or frame of reference.