Are cooking thermometers essential?

Thermometers are really practical when you do not have a lot of experience cooking things; it let you keep track of the proper food temperature.

For example, I do not cook beef roasts often, so I will use a thermometer to not mess up my cooking and waste a good amount of money on a good cut of meat.

Thermometers are essential for confectioneries where exact temperature are needed, mostly for sugar caramel stages.

Thermometers are also essential if you decide to try "molecular" cooking techniques with different chemicals; where temperature needs to be precise for certain reaction to happen (I do not have examples for that).

Cooking thermometers aren't essential, but they sure are damn useful. They simply take the guesswork out of temperature, which is of course critical to cooking. Why guess when that expensive steak is done to your liking when you can stick a $10 digital doohicky in there and be certain? Why do something incredibly dangerous like drop water in hot oil when you can use a thermometer?

Before a thermometer in my low-price oven, I didn't know if it was well calibrated or not. My mom's was way off, explaining some burns. I also adjusted the pre-heat oven time, sometimes completely unnecessary. I also found out that steps of 30 C/50 F are enough to adjust up or down, ignoring smaller 10 C/25 F intermediate steps.

Before a thermometer in my low-price refrigerator, I didn't realize I needed to adjust thermostat dial - and how much - depending on season in order to maintain the same temp. I also learned the various spots to organize what food goes where inside, sometimes contrary to what usual people say.

Before an infrared gun thermometer, I couldn't figure how high of a setting I could push my various non-stick pans on the stove top. I learned about checking frying oil temp in a flash, without immersion, if the bottom of the pan is dark as reflecting surfaces are not reliable for this type of reading.

Before a probe thermometer with wire, I had to rely on time per pounds, confused with what type of meat and which cut it was. With a stand-alone probe, I can double check the final results, or find out if I need more rotation time on my rotisserie.

Many more, but you got the point. However, a probe in a one inch thick steak on the pan on the stove is a bit of overkill.

This largely depends on what you cook, and how picky you are about the results.

If you cook steak and eggs type dishes, and aren't too picky about steak done-ness, then sure, skip the thermometer. Although I would definitely use one for steaks. But I'm very picky about how done my steak is.

Larger meats, such as roasts, I would consider a thermometer essential for. Time per pound is just too inaccurate, particularly given the different shapes of different cuts (or just different roasts). You want it even close to done correctly, your best bet is a thermometer.

As for baking, candying, etc.; it's certainly possible to manage without a thermometer, particularly if you're reasonably experienced, and again, if you're not too picky about exact results and/or not doing anything too cutting edge.

But I'd say it's similar to saying, can I cook without a measuring spoon? Sure, you can estimate the amount of flour in a loaf of bread, and if you're good at it you can probably get something that works and is decently tasty. But, will it turn out exactly right every time? Probably not. Even a loaf of bread is better with a thermometer, in fact!