[0n34n7]

Celsius is much more useful than stipulated here. For example, it takes 1J (Joule) to heat 1g (which is also 1ml) of pure water 1 degree Celsius.

The metric system is all weighted and related from temperature to mass to distance. This is what makes it so useful for Science, and frankly, every day use.

[kylec]

Please provide an example where you need to convert between Joules, grams, and Celsius in "every day use"

[fanf2]

Estimating how long it will take the kettle to boil :-)

[bramblerose]

One calorie, not one Joule. Water has a specific heat of ~4.2 kJ/kg.