Interesting idea. There's also the field of crisp-but-inaccurate notation. Don't know if they exist in the US but we have the 'gas mark' scale for ovens, so 'gas mark 6' means 'turn open the gas valve slightly more than half way' - the actual heat you get depends on the calorific value of the gas today (which doesn't vary hugely) and the placement of the item in the oven (which does, especially between ovens). And it's an open-loop control system so there's no feedback. But 'Gas mark 6 for half an hour' is probably accurate enough for most cooking once you've got used to the placement of things in your particular oven.
Another example is volume controls, which have a 'digital' display (number of bars) but an arbitrary scale.
One issue is this is hard to internationalise. (But how I hate the hieroglyphics that count as internationalisation on many appliances these days - washing machines are the worst)
Not true: there is (or can be) a crude control. If I monitor the gas flow in my oven simply by looking at the height of the flames: it starts with a low gas flow until proven to be ignited, then a high gas flow until temperature is reached, then a lower gas flow to maintain temperature.
Calibration is always wise, hence oven thermometers.
Here (US), ovens have been closed-loop systems for at least 50 years -- regardless if gas or electric.
Traditionally, the temperature controle was done with a fluid-filled "bulb" (closed system) whereby the liquid's expansion provided feedback of the current temperature inside the oven.
As Walter says, controls are "calibrated" in degrees (though there is a lot of hysteresis). The control's shaft is keyed so the knob is always aligned with the shaft in a fixed relationship. On the underside of the knob, a *mechanical* adjustment effectively allows the keyway to be rotated a small amount -- thereby allowing the numbers printed on the "knob"/dial to be moved relative to the control's shaft (I doubt many people are even aware of this capability and far fewer would ever consider *adjusting* the knobs to "calibrate" their ovens -- and then rkeeping track of which knob goes to which oven! (many stoves have dual ovens)
Instead, folks learn that their oven "runs cool" ("slow oven") or "hot".
Ovens here tend to have adjustable racks, inside. Most folks never/rarely move the rack from some nominal "centered" position (the positions have such delightfully "calibrated" markings as "A", "B", "C", and "D"). When the rack's position is adjusted, it is usually to accommodate something oversized (moving the rack downward) -- like a traditional Thanksgiving turkey.
Heat sources are available at the top and bottom of the oven. So, deciding where you want the heat to originate is also an option. E.g. "browning" the top (broil).
As most ovens contain two racks, bakers learn to use them to advantage by staggering "batches" within the oven. E.g. when I bake cookies, the heat source is from below so the first "sheet" of cookies goes on the lower rack. Halfway through the bake cycle, the first sheet is removed, spun through
180 degrees (left becomes right) and reinserted on the top rack while a new sheet is placed on the lower rack. The heat "seen" by the upper sheet is somewhat less direct than that below but each sheet of cookies experiences (basically) the same environment.
Calibration is important because Rx's ALWAYS indicate a temperature and a duration. E.g. 10 minutes at 400F. Changing either can have a marked effect on the outcome -- some Rx's simply can't tolerate high heat and have to be cooked on a "slow" oven.
350F probably being the most common setting for most things. I have baking Rx's that vary from 300-400 depending on the composition. Pizza is typically 450F. I've never seen anything lower than 250F.
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