Are cooking thermometers essential? I've been watching some cooking shows, and they seem very keen on there thermometers.
They have prob thermometers, oven thermometers, meat thermometers, confectionery thermometers, oil thermometers...
(Possibly these are all the same device, I don't know anything about kitchen thermometers).

Only thermometers I ever saw in real life, was my mother's roast thermometer (and I've made plenty of roasts without owning one), and her confectionery one that I broke as a child (and I've made plenty of toffee, with just the cold water test.)

So I've got on for quiet a while without owning one, and I've never seen one (out side of TV) used to check the oven temperature, or the oil temperature.

I'm wondering what the big deal is?
Will using the right temperature change my cooking? Am I perhaps doing something unsafe in using any of the many methods for estimating temperature?
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).